Spatial processor for enhanced performance in multi-talker speech displays

• US 7,391,877 B1
• Filed: 03/30/2007
• Issued: 06/24/2008
• Est. Priority Date: 03/31/2003
• Status: Expired due to Term

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Brungart, Douglas S.
• Primary Examiner(s): Chin; Vivian
• Assistant Examiner(s): Faulk; Devona E.
• Application Number:
  US11/731,561
• Time in Patent Office: 452 Days
• Field of Search: 381/93, 381/104, 381/107, 381/17, 381/309, 381/310, 381/1, 704/500.1, 704/250, 704/246, 704/200.1, 379/406.01, 379/202.01
• US Class Current: 381/310
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: H04S 2400/01 Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
• CPC Class Codes: H04S 2400/11 Positioning of individual sound objects, e.g. moving airplane, within a sound field H04S2420/13 takes precedence
• 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 7/302 Electronic adaptation of stereophonic sound system to listener position or orientation H04S7/301 takes precedence

Abstract

Optimal head related transfer function spatial configurations designed to maximize speech intelligibility in multi-talker speech displays by spatially separating competing speech channels combined with a method of normalizing the relative levels of the different talkers in a multi-talker speech display that improves overall performance even in conventional multi-talker spatial configurations.

Claims

1. An interference-minimizing and speech-intelligibility-maximizing head related transfer function (HRTF) spatial configuration method comprising the steps of:

receiving a plurality of speech input signals from competing talkers located at different source locations;

filtering said speech input signals with head-related transfer functions;

normalizing levels of said head related transfer functions from each source location whereby a speech-shaped noise input will produce the same level in the ear where the output is most intense at all of the source locations;

combining the outputs of said head related transfer functions; and

communicating outputs of said head related transfer functions to headphones of a system operator.

2. The interference-minimizing and speech-intelligibility-maximizing head related transfer function (HRTF) spatial configuration method of claim 1 further comprising the step of applying automatic gain control to each of said plurality of speech input signals.

3. The interference-minimizing and speech-intelligibility-maximizing head related transfer function (HRTF) spatial configuration method of claim 1 further comprising the step of system operator controlling relative levels of said competing talkers thereby providing the capability to amplify a single, important speech input signal.

4. An interference-minimizing and speech-intelligibility-maximizing head related transfer function spatial configuration method comprising the steps of:

receiving a plurality of speech input signals from competing talkers located at different source locations;

filtering said speech input signals with head-related transfer functions;

normalizing by taking the RMS of said head related transfer functions from each source location to set levels so a speech-shaped noise input will produce the same level of output at the ear where the output is most intense at all of the source locations with the highest RMS level at that location;

spatially configuring said head related transfer functions at azimuth angles of −

90 degrees, −

30 degrees, 0 degrees, 30 degrees and 90 degrees at a distance of 1 meter measured from center point of a head of each of said competing talkers;

locating additional head related transfer functions of said speech input signals at −

90 degrees and 90 degrees in azimuth at a distance of 12 cm from the center of the head;

means for digitally summing left head related transfer functions;

means for digitally summing right head related transfer function channels;

communicating outputs of said head related transfer functions to headphones of a system operator.

5. The interference-minimizing and speech-intelligibility-maximizing head related transfer function (HRTF) spatial configuration device of claim 4 further comprising a plurality of automatic gain control means for equalizing the levels of said speech input signals.

6. The interference-minimizing and speech-intelligibility-maximizing head related transfer function (HRTF) spatial configuration device of claim 4 further comprising means for operator selection for sending a speech input signal to a specific channel.

7. An interference-minimizing and speech-intelligibility-maximizing head related transfer function (HRTF) spatial configuration device comprising:

a plurality of simultaneous speech channels for communicating analog speech input signals;

a plurality of analog-to-digital converters receiving and converting output from said simultaneous speech channels;

two finite impulse response filters for normalizing output of said analog-to-digital converters by convolving each output from said analog-to-digital converters, said first finite impulse response filter coefficients representing left ear head related transfer functions from preselected talker locations and said second finite impulse response filter coefficients representing right ear head related transfer function from preselected talker locations whereby each talker will produce the same overall level in the selected ear where a continuous speech-shaped noise signal convolved with corresponding left and right ear head related transfer functions;

combining outputs of said left ear head related transfer functions;

combining outputs of said right ear head related transfer functions; and

communicating outputs of said left and right ear head related transfer functions to headphones of a system operator.

8. The interference-minimizing and speech-intelligibility-maximizing head related transfer function (HRTF) spatial configuration device of claim 7 further comprising an automatic gain control algorithm for equalizing speech input signals from said simultaneous speech channels.