Audio signal generator to emulate three-dimensional audio signals

• US 6,178,245 B1
• Filed: 04/12/2000
• Issued: 01/23/2001
• Est. Priority Date: 04/12/2000
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Sarain, Anthony Martin, Starkey, David Thomas
• Primary Examiner(s): Chang, Vivian
• Assistant Examiner(s): Mei, Xu
• Application Number:
  US09/548,077
• Time in Patent Office: 286 Days
• Field of Search: 381/1, 381/17-19, 381/309, 381/310, 381/300, 381/26, 381/74, 381/97-99, 381/320, 381/321, 381/FOR.126, 381/61, 381/63
• US Class Current: 381/17
• CPC Class Codes: H04S 2420/01 Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
• CPC Class Codes: H04S 5/00 Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation

Abstract

A system produces, based on samples of a single-channel input audio signal and an indication of a particular orientation of the listener relative to a source of the audio signal, a multi-channel output audio signal that emulates an audio signal as emanating from the source having the particular orientation to the listener. Interaural time delay (ITD) circuitry generates, from the single-channel input audio signal, a first left channel audio signal and a first right channel audio signal, wherein the first left channel audio signal and the first right channel audio signal are each based on the single-channel input audio signal but differ from each other at least with respect to phase based on the indication of the particular orientation. Azimuth frequency compensating (AFC) circuitry modifies the first left channel audio signal and the first right channel audio signal based on an azimuth, relative to the listener'"'"'s left ear and right ear, respectively, of the particular orientation. High frequency cuing (HFC) circuitry intensifies high frequencies of the first left channel audio signal and the first right channel audio signal based on whether the source is on axis with an ear canal of the listener'"'"'s left ear and right ear, respectively.

Claims

1. A system to produce, based on samples of a single-channel input audio signal and an indication of a particular orientation of the listener relative to a source of the audio signal, a multi-channel output audio signal that emulates an audio signal as emanating from the source having the particular orientation to the listener, the system comprising:

interaural time delay (ITD) circuitry that generates, from the single-channel input audio signal, a first left channel audio signal and a first right channel audio signal, wherein the first left channel audio signal and the first right channel audio signal are each based on the single-channel input audio signal but differ from each other at least with respect to phase based on the indication of the particular orientation;

azimuth frequency compensating (AFC) circuitry that modifies the first left channel audio signal and the first right channel audio signal based on an azimuth, relative to the listener'"'"'s left ear and right ear, respectively, of the particular orientation; and

high frequency cuing (HFC) circuitry that intensifies high frequencies of the first left channel audio signal and the first right channel audio signal based on whether the source is on axis with an ear canal of the listener'"'"'s left ear and right ear, respectively.

2. The system of claim 1, wherein the AFC circuit includes:

high pass filter circuitry;

low pass filter circuitry; and

filter control circuitry, the filter control circuitry controlling the high pass filter circuitry and the low pass filter circuitry based on the azimuth.

3. The system of claim 2, wherein the filter control circuitry operates based on control parameters empirically determined for the combinations of particular azimuth and elevation angles.

4. The system of claim 2, wherein:

the filter control circuitry operates based on entries in a filter control table, the filter control table including entries relating combinations of particular azimuth and elevation angles of the particular orientation to settings of the high pass filter circuitry and the low pass filter circuitry.

5. The system of claim 4, wherein the combinations of particular azimuth and elevation angles are in five-degree increments.

6. The system of claim 1, wherein:

the HFC circuitry includes an HFC volume table having entries for particular azimuth angles; and

the HFC circuitry intensifies the high frequencies based on the entry in the HFC volume table corresponding to the azimuth angle of the orientation.

7. The system of claim 1, wherein:

the ITD includes a read/write memory and pointer control circuitry to control read pointers into the read/write memory; and

the pointer control circuitry controls the read pointers based on an azimuth angle of the orientation.

8. The system of claim 7, wherein:

the indication of the particular orientation includes an indication of a velocity of movement of the source; and

the pointer control circuitry further controls the read pointers based on indication of velocity.

9. The system of claim 8, wherein the pointer control circuitry controls the read pointers based on the indication of velocity such that, as the velocity is increased, a rate of reading increases correspondingly.