Time processed head related transfer functions in a headphone spatialization system

• US 6,370,256 B1
• Filed: 03/31/1999
• Issued: 04/09/2002
• Est. Priority Date: 03/31/1998
• Status: Expired due to Term

• Current Assignee: Lake Technology Ltd. (Dolby Laboratories Incorporated)
• Original Assignee: Lake DSP Pty., Ltd.
• Inventors: McGrath, David Stanley
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): PENDLETON, BRIAN T
• Application Number:
  US09/283,664
• Time in Patent Office: 1,105 Days
• Field of Search: 381/309, 381/310
• US Class Current: 381/310
• CPC Class Codes: H04S 1/002 Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution control circuits for electronic adaptation of the sound field H04S7/30
• CPC Class Codes: H04S 1/005 For headphones
• 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 7/304 For headphones

Abstract

An apparatus for implementing a Head Related Transfer Function on an input audio signal in a headtracked listening environment comprising: a series of principle component filters attached to the input audio signal and each outputting a predetermined simulated sound arrival; a series of delay elements each attached to a corresponding one of the principle component filters and delaying the output of the filter by a variable amount depending on a delay input so as to produce a filter delay output; a summation means interconnected to the series of delay elements and summing the filter delay outputs to produce an audio speaker output signal; headtrack parameter mapping unit having a current orientation signal input and interconnected to each of the series of delay elements so as to provided the delay inputs.

Claims

1. An apparatus for implementing a Head Related Transfer Function on an input audio signal from a single sound source in a headtracked listening environment comprising:

a series of principal component filters attached to receive said input audio signal and each outputting a principal component corresponding to a portion of a predetermined simulated sound arrival from the sound source with the portions together forming said predetermined simulated sound arrival;

a series of delay elements each attached to a corresponding one of said principal component filters, each delay element being arranged to delay the output of said filter by a variable amount depending on a delay input so as to produce a filter delay output;

a summer interconnected to said series of delay elements and summing said filter delay outputs to produce a monaural audio speaker output signal; and

a headtrack parameter mapping unit having a current orientation signal input and interconnected to each of said series of delay elements so as to provide said delay inputs to said delay elements.

2. The apparatus of claim 1, wherein each of said delay elements further includes a gain factor unit adapted to multiply said filter delay output by an amount determined by a gain input signal to said delay element, with said headtrack parameter mapping unit being arranged to output said gain input signal to each of said gain factor units.

4. The apparatus of claim 1, wherein each one of the portions of the predetermined simulated sound arrival is representative of a different signal pathway between the single sound source and an ear of a listener.

5. The apparatus of claim 4, wherein at least some of the different signal pathways are reflected by the listener'"'"'s body.

6. The apparatus of claim 2, wherein the headtrack parameter mapping unit includes a lookup table which is arranged to output delay and gain values for an angle formed between the sound source and the orientation of the listener'"'"'s head.

3. A method of implementing a Head Related Transfer Function on an audio signal from a single sound source in a headtracked listening environment, said method comprising:

filtering said audio signal by a series of principal component filters to produce a series of filtered component outputs, each of said principal component filters outputting a portion of a predetermined simulated sound arrival from the sound source with the portions together forming said predetermined simulated sound arrival;

delaying each of said filtered component outputs by an amount dependent on a current listener'"'"'s head orientation so as to produce delayed principal components; and

combining said delayed principal components to form a monaural output audio speaker signal.

7. The method of claim 3, further comprising adjusting the gain of each one of said filtered component outputs by an amount dependent on a current listener'"'"'s head orientation so as to produce delayed principal components of differing amplitudes.

8. The method of claim 7, further comprising predetermining the delay of each one of the filtered components by measuring the delays for a series of particular head angles and storing the delays in a parameter mapping unit.

9. The method of claim 8, further comprising determining the current listener'"'"'s head orientation and outputting delay and gain values for an angle formed between the sound source and the orientation of the listener'"'"'s head.

10. The method of claim 3, wherein each delayed principal component is representative of each one of said different signal pathways between the single sound source and an ear of a listener.

11. The method of claim 10, wherein at least some of the different signal pathways are reflected by the listener'"'"'s body.