All The Claims

1. A ventilation air pressure oscillation mitigation device for a ventilator, the oscillation mitigation device comprising:
a housing defining an inlet and an outlet;
a valve seat defining a primary opening and a plurality of secondary openings;
a valve body selectively positionable in a first position and a second position,
wherein when the valve body is in the first position, substantially all of a first flow of ventilation air from the inlet to the outlet passes through the primary opening, and
wherein when the valve body is in the second position, all of a second flow of ventilation air from the inlet to the outlet passes through the plurality of secondary openings; and

an actuator for controlling a position of the valve body.
2. The ventilation air pressure oscillation mitigation device of claim 1, further comprising a filter media located proximate the plurality of second openings, such that when the valve body is in the second position, the second flow of ventilation air from the inlet to the outlet passes through the plurality of secondary openings and the filter media.
3. The ventilation air pressure oscillation mitigation device of claim 2, wherein the filter media is located upstream of the valve body.
4. The ventilation air pressure oscillation mitigation device of claim 1, wherein the actuator comprises a solenoid.
5. The ventilation air pressure oscillation mitigation device of claim 4, wherein the actuator further comprises a biasing element for holding the valve body in at least one of the first position and the second position.
6. The ventilation air pressure oscillation mitigation device of claim 5, wherein the biasing element comprises a magnet for holding the valve body in the first position.
7. The ventilation air pressure oscillation mitigation device of claim 6, wherein the biasing element further comprises a spring for holding the valve body in the second position.
8. A ventilator comprising an inspiratory limb and the ventilation air pressure oscillation mitigation device of claim 1, located on the inspiratory limb.

The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.

What is claimed is:

1. A method of processing a stored-value card request, comprising:
distributing a stored-value card to a first merchant for distribution to a customer having an account with a specific provider, the stored-value card having an associated identifier that can be used to associate a stored value with the card, the associated stored value being redeemable with one or more providers, including the specific provider, the account having an associated account number;
receiving a first request to activate the card from a first merchant terminal, the first request resulting from a card purchase transaction;
receiving a redemption request from the customer, wherein the redemption request comprises the identifier;
identifying the provider and the account number; and
passing from the central processor to the provider a first request to apply the associated stored value.
2. The method of claim 1, wherein the stored-value card is associated with the specific provider prior to receiving the first activation request.
3. The method of claim 1, wherein the associated value is printed on the card.
4. The method of claim 1, wherein the stored-value card has a face value.
5. The method of claim 1, wherein the first activation request is during the card purchase transaction.
6. The method of claim 1, further comprising:
prior to receiving the first activation request:
receiving a request for a card preauthorization confirmation from the first merchant terminal; and
passing the card preauthorization confirmation to the first merchant terminal.
7. The method of claim 1, wherein the first request to apply the associated stored value comprises a request to add the associated stored value to the account.
8. The method of claim 1, further comprising:
passing an activation confirmation to the first merchant terminal.
9. The method of claim 1, further comprising:
receiving a value insertion confirmation from the provider; and
passing to the customer confirmation information indicating that the associated value was added to the account.
10. The method of claim 1, wherein the first activation request comprises input information that was input from the card at the first merchant terminal.
11. The method of claim 10, wherein the card comprises a barcode, and the input information was input by scanning the barcode.
12. The method of claim 10, wherein the card comprises a magnetic strip, and the input information was input by swiping the magnetic strip.
13. The method of claim 1, wherein the identifier is printed on the card.
14. The method of claim 1, wherein the identifier is printed on the card, and wherein the identifier is not visible during the distributing action.
15. The method of claim 1, wherein the identifier is unique to the card.
16. The method of claim 1, wherein redemption instructions are printed on the card.
17. The method of claim 1, wherein the redemption request is received at a specific processor phone number, and wherein the provider is identified by the specific processor phone number.
18. The method of claim 1, wherein the redemption request is received at a specific website, and wherein the provider is identified by the specific website.
19. The method of claim 1, further comprising prompting the customer for card information.
20. The method of claim 1, wherein the identifier, a card number, and at least one of a barcode and a magnetic strip are on the card.
21. The method of claim 1, wherein the redemption request is received from a customer phone number, and the account number is identified by identifying the customer phone number using an automatic identification number (ANI) process.
22. The method of claim 1, further comprising:
determining whether the first merchant terminal is a trusted source of activation requests; and
activating the card.
23. The method of claim 1, further comprising:
determining whether the first activation request was received over a trusted communication network; and
activating the card.
24. The method of claim 1, further comprising:
determining whether the first merchant terminal is associated with the card; and
based on the determining action, activating the card.
25. The method of claim 1, further comprising:
prompting the customer for the identifier.
26. The method of claim 1, wherein the identifier is a PIN.
27. The method of claim 1, wherein the identifier is associated with the specific provider.
28. The method of claim 1, wherein the first request to apply the associated value comprises an .xml file conforming to an API of the specific provider.
29. The method of claim 1, wherein the first request to apply the associated value comprises an input into an IVR system of the specific provider.
30. The method of claim 1, further comprising:
based on receiving the first activation request, determining whether to activate the card.
31. The method of claim 30, further comprising:
after a determination to activate the card, associating the associated stored value with the identifier.
32. The method of claim 31, further comprising:
passing an activation confirmation to the first merchant terminal.
33. The method of claim 1, wherein the associated stored value is redeemable for wireless telephone service.
34. The method of claim 1, wherein the associated stored value is redeemable for paging services.
35. The method of claim 1, wherein the associated stored value is redeemable for internet-enabled communication services.
36. The method of claim 1, wherein the associated stored value is redeemable for wireless web access.
37. The method of claim 1, wherein the associated stored value is redeemable for emergency road service.
38. The method of claim 1, wherein the associated stored value is redeemable for at least one of legal service, account service, and tax service.
39. The method of claim 1, wherein the associated stored value is redeemable for transportation services.
40. The method of claim 1, wherein the associated stored value is redeemable for online dating services.
41. The method of claim 1, wherein the associated stored value is redeemable for internet access.
42. The method of claim 1, wherein the associated stored value is redeemable for film processing.
43. The method of claim 1, wherein the stored-value card is a gift card.
44. The method of claim 1, wherein the stored-value card is a prepaid gas card.
45. The method of claim 1, wherein the stored-value card is a prepaid grocery card.
46. The method of claim 1, wherein the stored-value card is a prepaid entertainment card.
47. The method of claim 1, wherein the stored-value card is a prepaid movie card.
48. The method of claim 1, wherein the stored-value card is a downloadable ring tone card.
49. The method of claim 1, wherein the stored-value card is a downloadable game card.
50. The method of claim 1, wherein the stored-value card is a downloadable movie card.
51. The method of claim 1, wherein the stored-value card is a downloadable music card.
52. The method of claim 1, wherein the stored-value card is a downloadable music card that uses at least one of MP3, MP4, WMV, and WAV music formats.
53. The method of claim 1, wherein the stored-value card is a customer rewards card.
54. The method of claim 1, wherein the stored-value card is at least one of a bridge and road toll card.
55. The method of claim 1, wherein the associated stored value is redeemable for long distance telephone communication.
56. The method of claim 1, wherein the associated stored value is redeemable for wireless communication.
57. The method of claim 1, further comprising:
associating the provider and the account number with the identifier in a record.
58. The method of claim 57, further comprising:
receiving a second request to activate the card at the central processor;
based on receiving the second request, identifying the account number and the provider by processing the record; and
passing a second request to process the associated stored value from the central processor to the provider.
59. The method of claim 58, further comprising:
based on receiving the second request, determining whether the account number and the provider have been previously identified.
60. The method of claim 58, wherein the second request to process the associated stored value comprises adding the associated stored value to the account.
61. The method of claim 58, wherein the second activation request is received from a second merchant terminal.
62. The method of claim 58, wherein the first merchant terminal is the second merchant terminal.
63. The method of claim 58, wherein the second activation request is received over the internet.
64. The method of claim 58, wherein the second activation request is received from a PDA.
65. The method of claim 58, wherein the second activation request is a request to add value to the account.
66. The method of claim 57, wherein the central processor stores the record in a database.
67. A method of processing a stored-value card request, comprising:
distributing a stored-value card to a first merchant for distribution to a customer having an account with a specific provider, the stored-value card having an associated identifier that can be used to associate a stored value with the card, the associated stored value being redeemable with one or more providers, including the specific provider, the account having an associated account number;
receiving a first request to activate the card from a first merchant terminal, the first request resulting from a card purchase transaction;
receiving a redemption request from the customer, wherein the redemption request comprises the identifier;
identifying the provider and the account number;
associating the provider and the account number with the identifier in a record;
applying the associated value to the account based on the redemption request;
receiving at the central processor a second request to activate the card; and
applying the associated value to the account based on the second activation request.
68. The method of claim 67, further comprising:
based on receiving the second activation request, automatically identifying the provider and the account number by processing the record,
wherein applying the associated value to the account based on the second activation request is additionally based on automatically identifying the provider and the account number.
69. The method of claim 67, further comprising:
based on receiving the second activation request, determining whether the account number and the provider have been previously identified.
70. The method of claim 67, wherein the action of applying the associated value to the account based on the second activation request comprises adding the associated stored value to the account.
71. The method of claim 67, wherein the central processor manages the account.
72. The method of claim 67, wherein the stored-value card is associated with the specific provider prior to receiving the first activation request.
73. The method of claim 67, wherein the associated value is printed on the card.
74. The method of claim 67, wherein the stored-value card has a face value.
75. The method of claim 67, wherein the first activation request is during the card purchase transaction.
76. The method of claim 67, further comprising:
prior to receiving the first activation request:
receiving a request for a card preauthorization confirmation from the first merchant terminal; and
passing the card preauthorization confirmation to the first merchant terminal.
77. The method of claim 67, wherein the first request to apply the associated stored value comprises a request to add the associated stored value to the account.
78. The method of claim 67, further comprising:
passing an activation confirmation to the first merchant terminal.
79. The method of claim 67, further comprising:
receiving a value insertion confirmation from the provider; and
passing to the customer confirmation information indicating that the associated value was added to the account.
80. The method of claim 67, wherein the first activation request comprises input information that was input from the card at the first merchant terminal.
81. The method of claim 80, wherein the card comprises a barcode, and the input information was input by scanning the barcode.
82. The method of claim 80, wherein the card comprises a magnetic strip, and the input information was input by swiping the magnetic strip.
83. The method of claim 67, wherein the identifier is printed on the card.
84. The method of claim 67, wherein the identifier is printed on the card, and wherein the identifier is not visible during the distributing action.
85. The method of claim 67, wherein the identifier is unique to the card.
86. The method of claim 67, wherein redemption instructions are printed on the card.
87. The method of claim 67, wherein the redemption request is received at a specific processor phone number, and wherein the provider is identified by the specific processor phone number.
88. The method of claim 67, wherein the redemption request is received at a specific website, and wherein the provider is identified by the specific website.
89. The method of claim 67, further comprising prompting the customer for card information.
90. The method of claim 67, wherein the identifier, a card number, and at least one of a barcode and a magnetic strip are on the card.
91. The method of claim 67, wherein the redemption request is received from a customer phone number, and the account number is identified by identifying the customer phone number using an automatic identification number (ANI) process.
92. The method of claim 67, further comprising:
determining whether the first merchant terminal is a trusted source of activation requests; and
activating the card based on the determining action.
93. The method of claim 67, further comprising:
determining whether the first activation request was received over a trusted communication network; and
activating the card based on the determining action.
94. The method of claim 67, further comprising:
determining whether the first merchant terminal is associated with the card; and
based on the determining action, activating the card.
95. The method of claim 67, further comprising:
prompting the customer for the identifier.
96. The method of claim 67, wherein the identifier is a PIN.
97. The method of claim 67, wherein the identifier is associated with the specific provider prior to the first activation request.
98. The method of claim 67, wherein the first request to apply the associated value comprises an .xml file conforming to an API of the specific provider.
99. The method of claim 67, wherein the first request to apply the associated value comprises an input into an IVR system of the specific provider.
100. The method of claim 67, further comprising:
based on receiving the first activation request, determining whether to activate the card.
101. The method of claim 100, further comprising:
after a determination to activate the card, associating the associated stored value with the identifier.
102. The method of claim 67, further comprising:
passing an activation confirmation to the first merchant terminal.
103. The method of claim 67, wherein the associated stored value is redeemable for wireless telephone service.
104. The method of claim 67, wherein the associated stored value is redeemable for paging services.
105. The method of claim 67, wherein the associated stored value is redeemable for internet-enabled communication services.
106. The method of claim 67, wherein the associated stored value is redeemable for wireless web access.
107. The method of claim 67, wherein the associated stored value is redeemable for emergency road service.
108. The method of claim 67, wherein the associated stored value is redeemable for at least one of legal service, account service, and tax service.
109. The method of claim 67, wherein the associated stored value is redeemable for transportation services.
110. The method of claim 67, wherein the associated stored value is redeemable for online dating services.
111. The method of claim 67, wherein the associated stored value is redeemable for internet access.
112. The method of claim 67, wherein the associated stored value is redeemable for film processing.
113. The method of claim 67, wherein the stored-value card is a gift card.
114. The method of claim 67, wherein the stored-value card is a prepaid gas card.
115. The method of claim 67, wherein the stored-value card is a prepaid grocery card.
116. The method of claim 67, wherein the stored-value card is a prepaid entertainment card.
117. The method of claim 67, wherein the stored-value card is a prepaid movie card.
118. The method of claim 67, wherein the stored-value card is a downloadable ring tone card.
119. The method of claim 67, wherein the stored-value card is a downloadable game card.
120. The method of claim 67, wherein the stored-value card is a downloadable movie card.
121. The method of claim 67, wherein the stored-value card is a downloadable music card.
122. The method of claim 67, wherein the stored-value card is a downloadable music card that uses at least one of MP3, MP4, WMV, and WAV music formats.
123. The method of claim 67, wherein the stored-value card is a customer rewards card.
124. The method of claim 67, wherein the stored-value card is at least one of a bridge and road toll card.
125. The method of claim 67, wherein the associated stored value is redeemable for long distance telephone communication.
126. The method of claim 67, wherein the associated stored value is redeemable for wireless communication.
127. The method of claim 58, wherein the central processor stores the record in a database.
128. The method of claim 58, wherein the second activation request is received from a second merchant terminal.
129. The method of claim 58, wherein the first merchant terminal is the second merchant terminal.
130. The method of claim 58, wherein the second activation request is received over the internet.
131. The method of claim 58, wherein the second activation request is received from a PDA.
132. The method of claim 58, wherein the second activation request is a request to add value to the account.
133. The method of claim 67, wherein the associated stored value is redeemable for at least one of a plurality of different types of prepaid services.
134. A system for adding stored value to a customer account, comprising:
a stored-value card having an associated stored value redeemable with any of a plurality of providers, wherein the stored-value card comprises an identifier and an indicia of the identifier;
a merchant terminal configured to input an indicia of an identifier associated with a stored-value card and transmit the indicia to a central processor during a stored-value card transaction with a customer having a stored-value account with a specific provider;
a central processor configured to:
receive an indicia of an identifier from a merchant terminal, wherein the indicia is associated with a specific stored-value card;
receive an identifier from a customer, wherein the identifier is associated with the specific stored-value card;
identify a provider and a customer account number associated with the specific stored-value card; and
pass a first request to process the associated stored value from the central processor to a specific provider, wherein the specific provider is configured to modify the customer account based on the request; and

a provider configured to receive from the central processor requests to add value to a customer account.
135. The system of claim 134, wherein the central processor is further configured to:
associate a provider and an account number with an indicia in a record;
automatically identify an account and provider based on receiving an indicia of a card for which the central processor has already passed a request to a provider to add an associated value to an account with the provider; and
after identifying the account and the provider, automatically pass from the central processor to the identified provider a second request to add the associated value to the account, wherein the provider is configured to modify the customer account based on the request.
136. A method of processing a stored-value card request, comprising:
distributing a stored-value card to a first merchant for distribution to a customer having an account with a specific provider, the stored-value card having an associated identifier that can be used to activate the card and associate a stored value with the card, the associated stored value being redeemable with one or more providers, including the specific provider, the account having an associated account number;
receiving a first request to activate the card at a central processor from a first merchant terminal, the first request resulting from a card purchase transaction;
passing an identifier from the central processor to the merchant terminal for distribution to the customer;
receiving a redemption request from the customer, wherein the redemption request comprises the identifier;
identifying the provider and the account number; and
passing a first request to apply the associated stored value from the central processor to the provider.
137. A method of processing a stored-value card request, comprising:
distributing a stored-value card to a first merchant for distribution to a customer having an account with a specific provider, the account having an associated account number;
receiving a first request to activate the card from a first merchant terminal, the first request resulting from a card purchase transaction;
passing an identifier to the merchant terminal for distribution to the customer, the identifier being associated with the card and operative to associate a stored value with the card, the associated stored value being redeemable with one or more providers, including the specific provider,
receiving a redemption request from the customer, wherein the redemption request comprises the identifier;
identifying the provider and the account number; and
passing a first request to apply the associated stored value from the central processor to the provider.
138. A method of processing a stored-value card request, comprising:
distributing a stored-value card from a central processor to a first merchant for distribution to a customer having an account with a provider, the stored-value card having an associated identifier and an associated stored value, the associated stored value being redeemable with one or more providers, the account having an associated account number;
receiving a first request to activate the card from a first merchant terminal;
receiving a redemption request from the customer, wherein the redemption request comprises the identifier;
identifying the provider and the account number;
associating the provider and the account number with the identifier in a record;
modifying the account based on the redemption request;
receiving a subsequent request to activate the card at the central processor; and
modifying the account based on the second request to activate.
139. A method of processing a stored-value card request, comprising:
distributing a stored-value card to a first merchant for distribution to a customer having an account with a specific provider, the stored-value card having an associated identifier that can be used to associate a stored value with the card, the associated stored value being redeemable with one or more providers, including the specific provider, the account having an associated account number;
receiving a first request to activate the card from a first merchant terminal;
receiving a redemption request from the customer, wherein the redemption request comprises the identifier;
identifying the provider and the account number;
associating the provider and the account number with the identifier in a record;
causing the associated value to be added to the account based on the redemption request;
receiving at the central processor a second request to activate the card; and
causing the associated value to be added to the account based on the second activation request.
140. The method of claim 139, wherein the action of causing the associated value to be added to the account based on the redemption request comprises passing from the central processor to a specific one of the one or more providers a request to add value to the account.
141. The method of claim 139, wherein the action of causing the associated value to be added to the account based on the redemption request comprises applying the associated value to the account.

1. A salicide process, comprising:
forming a metal layer over a silicon layer, wherein the metal layer is selected from a group consisting of titanium, cobalt, platinum, palladium and an alloy thereof;
performing a first thermal process; and
performing a second thermal process, wherein the second thermal process comprises a first step performed at 600\u02dc700 degrees centigrade for 1 0\u02dc60 seconds and a second step performed at 750\u02dc850 degrees centigrade for 1 0\u02dc60 seconds.
2. The salicide process according to claim 1, wherein the first step of the second thermal process is performed at 630\u02dc670 degrees centigrade for 20\u02dc40 seconds.
3. The salicide process according to claim 1, wherein the second step of the second thermal process is performed at 780\u02dc820 degrees centigrade for 20\u02dc40 seconds.
4. The salicide process according to claim 1, wherein the first thermal process is a one-step thermal process.
5. The salicide process according to claim 4, wherein the one-step thermal process performed at 450\u02dc550 degrees centigrade for 1 0\u02dc60 seconds.
6. The salicide process according to claim 1, wherein the first and second steps of the second thermal process is a rapid thermal annealing process, respectively.
7. The salicide process according to claim 1, wherein the first thermal process is a rapid thermal annealing process.
8. The salicide process according to claim 1, further comprising performing a selective etching step before the second thermal process is performed.
9. A salicide process, comprising:
forming a metal layer over a silicon layer, wherein the metal layer is selected from a group consisting of nickel and an alloy thereof;
performing a first thermal process; and
performing a second thermal process, wherein the second thermal process comprises a first step performed at 300\u02dc400 degrees centigrade for 1 0\u02dc60 seconds and a second step performed at 450\u02dc550 degrees centigrade for 1 0\u02dc60 seconds.
10. The salicide process according to claim 9, wherein the first step of the second thermal process is performed at 330\u02dc370 degrees centigrade for 20\u02dc40 seconds.
11. The salicide process according to claim 9, wherein the second step of the second thermal process is performed at 480\u02dc520 degrees centigrade for 20\u02dc40 seconds.
12. The salicide process according to claim 9, wherein the first thermal process is a one-step thermal process.
13. The salicide process according to claim 12, wherein the one-step thermal process performed at 250\u02dc400 degrees centigrade for 1 0\u02dc60 seconds.
14. The salicide process according to claim 9, wherein the second thermal process is a rapid thermal annealing process.
15. The salicide process according to claim 9, wherein the first and second steps of the second thermal process is a rapid thermal annealing process, respectively.
16. The salicide process according to claim 9, further comprising performing a selective etching step before the second thermal process is performed.

The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.

1. A method of creating a surround experience for headphones, the method comprising:
receiving a first input audio channel signal and a second input audio channel signal;
splitting each of the first and second input audio channel signals into a high-pass audio signal and a low-pass audio signal;
cross-mixing the low-pass audio signal of the first input audio channel signal and the low-pass audio signal of the second input audio channel signal;
adjusting each of the low-pass audio signals by applying artificial reverberation, wherein the applying artificial reverberation comprises applying a different delay profile to each of the low-pass audio signals;
adding the high-pass audio signal and the adjusted and cross-mixed low-pass audio signal for each of the first and second input audio channel signals to generate a first output audio channel signal and a second output audio channel signal.
2. The method of claim 1 wherein the splitting is performed by a first audio crossover for the first input audio channel signal and by a second audio crossover for the second input audio channel signal, wherein each of the first and second audio crossovers is implemented using a second order infinite impulse response low-pass filter.
3. The method of claim 1 wherein the artificial reverberation is applied to each of the low-pass audio signals after the cross-mixing.
4. The method of claim 1 wherein the artificial reverberation is applied using a plurality of all-pass filters in series, wherein the applying the different delay profile to each of the low-pass audio signals comprises applying different delays at different positions in the series of all-pass filters between each of the low-pass audio signals.
5. The method of claim 1 wherein the applying artificial reverberation comprises:
applying a first delay profile to the low-pass audio signal of the first input audio channel signal using one or more all-pass filters; and
applying a second delay profile to the low-pass audio signal of the second input audio channel signal using one or more all-pass filters;
wherein the first delay profile is different from the second delay profile.
6. The method of claim 5 wherein the one or more all-pass filters used to apply the first delay profile are Schroeder all-pass filters, and wherein the one or more all-pass filters used to apply the second delay profile are Schroeder all-pass filters.
7. The method of claim 1 wherein the applying artificial reverberation comprises:
for the low-pass audio signal of the first input audio channel signal, passing the low-pass audio signal through a series of three Schroeder all-pass filters, wherein each of the three Schroeder all-pass filters introduces a delay;
for the low-pass audio signal of the second input audio channel signal, passing the low-pass audio signal through a series of three Schroeder all-pass filters, wherein each of the three Schroeder all-pass filters introduces a delay corresponding to the delay introduced by the Schroeder all-pass filter of the low-pass audio signal of the first input audio channel signal at the same stage of the series;
wherein one of the three Schroeder all-pass filters for the low-pass audio signal of the first input audio channel signal introduces a small additional delay when passing the low-pass audio signal through the series of three Schroeder all-pass filters;
wherein one of the three Schroeder all-pass filters for the low-pass audio signal of the second input audio channel signal introduces the small additional delay when passing the low-pass audio signal through the series of three Schroeder all-pass filters, wherein the small additional delay for the low-pass audio signal of the second input audio channel signal is introduced using a Schroeder all-pass filter at a different stage of the series than the small additional delay for the low-pass audio signal of the first input audio channel signal.
8. The method of claim 7 further comprising:
receiving a user-settable parameter used to control the small additional delay.
9. The method of claim 1 further comprising:
receiving a user-settable parameter that controls the cross-mixing by indicating an amount of channel cross-mixing to apply between the low-pass audio signal of the first input audio channel signal and the low-pass audio signal of the second input audio channel signal.
10. The method of claim 1, wherein the method is performed using integer calculations.
11. The method of claim 1, wherein the method is implemented by a portable computing device.
12. One or more computer-readable media comprising computer-executable instructions for causing a computing device to perform the method of claim 1.
13. A system for creating a surround experience for headphones, the system comprising:
an input module for receiving two input audio channel signals;
a crossover module for splitting each channel signal of the two input audio channel signals into a high-pass audio signal and a low-pass audio signal;
a channel cross-mixing module for cross-mixing the low-pass audio signals;
a reverberation module for applying artificial reverberation to each of the cross-mixed low-pass audio signals, wherein the reverberation module applies a different delay profile to each of the low-pass audio signals;
an adder module for combining the high-pass audio signal and the reverberation-applied and cross-mixed low-pass audio signal for each channel signal of the two input audio channel signals to generate two output audio channel signals.
14. The system of claim 13 wherein the crossover module comprises an audio crossover for each channel signal of the two input audio channel signals, and wherein each crossover is implemented using a second order infinite impulse response low-pass filter.
15. The system of claim 13 wherein the reverberation module comprises a plurality of Schroeder all-pass filters in series for each of the cross-mixed low-pass audio signals, wherein applying the different delay profile to each of the low-pass audio signals comprises applying different delays at different positions in the series of Schroeder all-pass filters between each of the low-pass audio signals.
16. The system of claim 13 wherein the reverberation module comprises:
two sets of three Schroeder all-pass filters in series, one set for each of the low-pass audio signals, for introducing delay in each of the low-pass audio signals, wherein delay amount is different between corresponding Schroeder all-pass filters in the series for each of the low-pass audio signals.
17. The system of claim 13 further comprising:
a user input module for receiving a user-settable parameter used to control a delay amount applied by the reverberation module.
18. The system of claim 13 further comprising:
a user input module for receiving a user-settable parameter that controls the cross-mixing by indicating an amount of cross-mixing between the low-pass audio signals.
19. A system for creating a surround experience for headphones, the system comprising:
an input module for receiving a mono input audio channel signal;
a crossover module for splitting the mono input audio channel signal into a high-pass audio signal and a low-pass audio signal;
a reverberation module for applying artificial reverberation to two copies of the low-pass audio signal, wherein the reverberation module applies a different delay profile to each copy of the low-pass audio signal, and wherein the reverberation module produces a left and right low-pass audio signal; and
an adder module for combining the high-pass audio signal with each of the left and right low-pass audio signals to generate left and right output audio channel signals.
20. The system of claim 19 wherein the reverberation module comprises:
two sets of three Schroeder all-pass filters in series, one set for each copy of the low-pass audio signal, for introducing delay in each copy of the low-pass audio signal, wherein delay amount is different between corresponding Schroeder all-pass filters in the series for each copy of the low-pass audio signal.