CA2579463A1

CA2579463A1 - Program or method and device for detecting an audio component in ambient noise samples

Info

Publication number: CA2579463A1
Application number: CA002579463A
Authority: CA
Inventors: Martin Bichsel
Original assignee: Individual
Current assignee: GfK Switzerland AG
Priority date: 1997-06-23
Filing date: 1998-06-22
Publication date: 1998-12-23
Anticipated expiration: 2018-06-22
Also published as: CA2579463C

Abstract

The amount of data produced in the process of recording even short hearing samples by means of a monitor may be considerably reduced by effecting a normalization to a range of values D and a subsequent nonlinear mapping to a second, preferably smaller range of values W. The result may be stored in an electronic memory. Further preferred measures are the splitting of the hearing samples into e.g. 6 signals each of which contains a respective frequency band of the original signal, and the conversion of the original amplitude values into energy variation values with simultaneous low pass filtering.
Preferably, all cited processing steps are performed by a signal processor. A
continuous recording time of up to 14 days by a monitor in the form of a wristwatch can thus be attained with state-of-the-art technology.

Claims

1. Method for evaluating recorded hearing samples recorded by at least one first device, the method comprising recording, by a second device, a plurality of samples of programs to be monitored wherein each of the samples of programs to be monitored has a greater duration than a corresponding one of the recorded hearing samples, and calculating a first correlation for comparing the hearing samples with the program samples in order to find a match.

2. The method of claim 1, wherein the recording of the program samples is started sufficiently before the hearing samples and the program sample recording is sufficiently longer than that of the hearing samples to ensure that in the correlation, time shifts between the hearing samples and the program samples can be compensated by a displacement in time of the hearing samples with respect to the program samples.

3. The method of claim 1, wherein said first correlation is a standard correlation according to the formula N: number of values of the hearing sample which are used in the correlation, t: time shift s i: hearing sample value at the time i, m i-t: program sample value at the time i-t, c i: correlation value for the time shift t: -1<=ct<=1.

4. The method of claim 2, wherein the comparison of the hearing samples with the program samples is effected in two passes, wherein a first pass comprises comparing a respective hearing sample to all program samples using said first correlation, the calculation of which uses coarse graduation of the time shift, and wherein a second pass comprises using a second, more rugged correlation which provides a finer graduation of the time shift.

5. The method of claim 4, wherein the second correlation is used in the case where the first correlation yields a correlation value c t above a predetermined value for a time shift.

6. The method of claim 4, wherein the second correlation provides a resolution of the time shift which is at least twice as high as that obtained with the first correlation.

7. The method of claim 4, wherein said second correlation is chosen such that great deviations between the hearing and the program sample have a smaller influence upon the correlation coefficients than the first correlation.

8. The method of claim 4, wherein said second correlation is effected according to the formula wherein N: number of hearing sample values used in the correlation, t: time shift between the hearing and the program sample, S i : hearing sample value at the time i, m i-t: program sample value at the time i-t, and a: scaling factor which takes account of the damping of the program signal with respect to the hearing sample;

r t: correlation value for the shift t, 0 (optimal correlation) < r t <1 (no correlation), a being determined in such a manner that r t assumes a minimal value.

9. The method of claim 4, wherein the first correlation is a standard correlation according to the formula N: number of values of the hearing sample which are used in the correlation, t: time shift s i: hearing sample value at the time i, m i-t: program sample value at the time i-t, c i: correlation value for the time shift t: -1<=c t<=1.

10. The method of claim 1, wherein the hearing samples are obtained by:
periodically recording samples of an ambient noise using a sound transducer, the sample duration being shorter than the sampling cycle;

normalizing the amplitude of the recorded audio signal within a first predetermined range D;

mapping the normalized amplitude values of the audio signal onto a second predetermined range of values in the time domain using a non-linear mapping function to obtain an emphasis of selected values ranged within the first or the second predetermined ranges.

11. The method of claim 1, wherein the hearing sample values are integer binary numbers having a fixed number of binary digits (bits) from 3 to 16.

12. The method of claim 11, where the number of digits is from 4 to 8.

13. A computer program which when run on a computer executes the method of evaluating recorded hearing samples recorded by at least one first device, the method comprising recording, by a second device, a plurality of samples of programs to be monitored wherein each of the samples of programs to be monitored has a greater duration than a corresponding one of the recorded hearing samples, and calculating a first correlation for comparing the hearing samples with the program samples in order to find a match.

14. A data carrier with the computer program of claim 13.