SPECTRAL OPTIMIZATION OF AUDIO MASKING WAVEFORMS

• US 20180357995A1
• Filed: 06/07/2017
• Published: 12/13/2018
• Est. Priority Date: 06/07/2017
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Lee, Daniel K., Gauger, JR., Daniel M., Wax, Aric J.
• Granted Patent: US 10,360,892 B2
• Time in Patent Office: Days
• CPC Class Codes: G10K 11/1752 Masking
• CPC Class Codes: G10K 11/178 by electro-acoustically regenerating the original acoustic waves in anti-phase
• CPC Class Codes: G10K 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/3011 Single acoustic input
• CPC Class Codes: G10K 2210/3028 Filtering, e.g. Kalman filters or special analogue or digital filters
• CPC Class Codes: G10L 25/18 the extracted parameters being spectral information of each sub-band
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06
• CPC Class Codes: H04R 2420/07 Applications of wireless loudspeakers or wireless microphones
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones

Abstract

A system for masking audio signals includes a microphone for generating an ambient audio signal representing ambient noise, a speaker for rendering masking audio, and a processor in communication with the microphone and the speaker. The processor performs spectral analysis on the ambient audio signal from the microphone to determine a spectral envelope of the ambient noise, adjusts a frequency response of an optimizing filter based on the spectral envelope, applies the optimizing filter to a baseline masking waveform, producing an output waveform with relative spectral distribution matching the ambient noise, and provides the output waveform to the speaker.

Claims

1. A system for masking audio signals, the system comprising:

a microphone for generating an ambient audio signal representing ambient noise;

a speaker for rendering masking audio;

a processor in communication with the microphone and the speaker, and configured to;

store a measurement of the ambient audio signal from the microphone;

perform spectral analysis on the stored ambient audio signal to determine a spectral envelope of the ambient noise,

based on the spectral envelope, adjust a frequency response of an optimizing filter,

apply the optimizing filter to a baseline masking waveform, producing an output waveform with relative spectral distribution matching the ambient noise, and

provide the output waveform to the speaker,

wherein, the step of storing the measurement of the ambient audio signal is repeated on a periodic basis and averaged over a first time period to produce a long-term composite measurement,

the spectral analysis, frequency response adjustment, and application of the optimizing filter, to produce the output waveform is performed on a long-term composite measurement of the ambient audio signal.

2. The system of claim 1, wherein the periodic basis is every five minutes.

3. The system of claim 1, wherein the long-term composite measurement of the ambient audio signal over at least a first night is used to produce an output waveform for use on subsequent nights.

4. The system of claim 1, wherein one or more of the processor tasks are performed by a portable computing device,

results of those tasks being transferred to the earbud, the remainder of the processor tasks being performed in the earbud.

5. The system of claim 4, wherein the spectral analysis and the adjusting of the frequency response of the optimizing filter are performed in the portable computing device, the adjustment to the optimizing filter is provided to the earbud, and the application of the filter is performed in the earbud.

6. A method of masking audio signals, the method comprising:

receiving an ambient audio signal representing ambient noise from a microphone;

storing a measurement of the ambient audio signal from the microphone;

performing spectral analysis on the stored ambient audio signal to determine a spectral envelope of the ambient noise;

based on the spectral envelope, adjusting a frequency response of an optimizing feature;

applying the optimizing filter to a baseline masking waveform, producing an output waveform with relative spectral distribution matching the ambient noise; and

providing the output waveform to a speaker;

wherein, the step of storing the measurement of the ambient audio signal is repeated on a periodic basis and averaged over a first time period to produce a long-term composite measurement,

the spectral analysis, frequency response adjustment, and application of the optimizing filter to produce the output waveform is performed on a long-term composite measurement of the ambient audio signal.

7. The method of claim 6, wherein performing the spectral analysis comprises:

applying a discrete fast-Fourier transform (DFFT) to a digital representation of the long-term average ambient audio signal, the DFFT output consisting of a plurality of frequency bins;

using the values in the DFFT output bins as representations of the magnitude of the ambient sound in each of a plurality of frequency bands corresponding to the frequency bins;

combining the magnitudes to form a spectral mask of the ambient noise over the audio band; and

normalizing and scaling the spectral mask to generate adjustment coefficients of the optimizing filter.

8. The method of claim 6, wherein the periodic basis is every five minutes.

9. The method of claim 6, wherein the long-term composite measurement of the ambient audio signal over at least a first night is used to produce an output waveform for use on subsequent nights.

10. The method of claim 6, wherein one or more of the steps are performed by a portable computing device, and

results of those tasks are transferred to the earbud, the remainder of the processor tasks being performed in the earbud.

11. The method of claim 6, wherein the spectral analysis and the adjusting of the frequency response of the optimizing filter are performed in the portable computing device, the adjustment to the optimizing filter is provided to the earbud, and the application of the filter is performed in the earbud.