Method of signal processing for maintaining directional hearing with hearing aids
First Claim
1. A method for obtaining coefficients of a digital filter for use in compensating effects of a hearing aid, comprising the steps of:
- determining an unaided head related transfer function for each ear and for a plurality of azimuth locations of a sound source;
determining an aided head related transfer function for each ear having a hearing aid installed thereat and for the plurality of azimuth locations of the sound source;
finding a minimum phase representation of the unaided head related transfer function;
finding a minimum phase representation of the aided head related transfer function;
calculating the ratio between the unaided minimum phase representation and the aided minimum phase representation to form a target filter response; and
obtaining a plurality of filter coefficients by sampling the target filter response at a plurality of frequency values corresponding to frequency increments in the digital filter.
2 Assignments
0 Petitions
Accused Products
Abstract
The insertion effects of hearing aids are determined and compensated to restore the ability to have directional hearing in individuals wearing hearing aids. In one aspect a method involves finding the ratio of the unaided head related transfer function to the aided head related transfer function and then designing a hearing aid filter that is the inverse of that derived insertion effect, thereby restoring the ability to hear interaural differences in aided systems both in level and in time of arrival to improve hearing in the presence of noise. The insertion effects can be derived either through frequency domain analyses, using the above-mentioned transfer function calculations and measurements, or in another aspect through time domain analyses, using optimal filter calculations and measurement obtained using a successive data acquisition system that is subsequently time aligned by recording trigger pulses with the data.
-
Citations
27 Claims
-
1. A method for obtaining coefficients of a digital filter for use in compensating effects of a hearing aid, comprising the steps of:
-
determining an unaided head related transfer function for each ear and for a plurality of azimuth locations of a sound source; determining an aided head related transfer function for each ear having a hearing aid installed thereat and for the plurality of azimuth locations of the sound source; finding a minimum phase representation of the unaided head related transfer function; finding a minimum phase representation of the aided head related transfer function; calculating the ratio between the unaided minimum phase representation and the aided minimum phase representation to form a target filter response; and obtaining a plurality of filter coefficients by sampling the target filter response at a plurality of frequency values corresponding to frequency increments in the digital filter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A method for selecting filter coefficients in a digital filter for use in compensating loss of directional information to a wearer of a hearing aid, comprising the steps of:
-
determining an unaided head related transfer function using a binaural manikin for each ear and for a plurality of azimuth locations of a sound source; determining an aided head related transfer function using a hearing aided binaural manikin for each ear and for the plurality of azimuth locations of the sound source; finding a minimum phase representation of the unaided head related transfer function; finding a minimum phase representation of the aided head related transfer function; finding the ratio of the unaided minimum phase representation to the aided minimum phase representation; and obtaining a plurality of filter coefficients by sampling the target filter response at a plurality of frequency values corresponding to frequency increments in the digital filter. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
-
-
21. A method for obtaining coefficients of a digital filter for use in compensating effects of a hearing aid, comprising the steps of:
-
producing an audio signal having a predetermined frequency content at a predetermined sound pressure level at a first time; producing a trigger pulse simultaneously with the audio signal; detecting the produced signal at an eardrum location in the absence of a hearing aid and recording the detected signal in synchronism with the trigger pulse on a first track of a magnetic tape; inserting a hearing aid adjacent the eardrum location; producing the audio signal at a second, later time; producing the trigger pulse simultaneously with the audio signal the second time; detecting the produced signal at the eardrum location in the presence of the hearing aid and recording the detected signal in synchronism with the trigger pulse on a second track of a magnetic tape in time alignment with the onset of the recorded signal in the first track by aligning the recorded trigger pulse; sampling the signals recorded in the first and second tracks; and calculating digital filter coefficients from the sampled signals using discrete-time Wiener equations. - View Dependent Claims (22, 23, 24, 25, 26, 27)
-
Specification