Electrical audio signal processing systems and devices – One-way audio signal program distribution – Public address system
Patent
1989-10-25
1991-05-07
Kemeny, E. S.
Electrical audio signal processing systems and devices
One-way audio signal program distribution
Public address system
73585, 381 682, 128746, G10L 500
Patent
active
050143182
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field of the Invention
The present invention relates to an apparatus for checking audio signal processing systems.
In processing audio signals, by way of illustration in digital coding for data reduction, in reproducing recorded signals via loudspeakers, etc., errors occur, i.e. the processed audio signal deviates from the original audio signal. Such deviations are partially audible, partially inaudible due to the characteristics of the human sense of hearing.
Particularly, the new processes of encoding audio signals make use of the characteristics of the human sense of hearing: only those parts of the signal are transmitted exactly that the human ear can readily hear. The spectral composition of the "error or disturbance" resulting from the "inexact" transmission is influenced in such a manner that is inaudible or barely audible. High compression degrees of 80% to 90% desired for digital transmission of audio signals, by way of illustration via digital radio stations or for digital storage, can be achieved only by this means.
2. State of the Art
If pieces of music are digitally encoded for data reduction and subsequently decoded, by means of conventional measuring processes, such as S/N measurements (measurement of the signal
oise ratio) or harmonic distortion coefficient measurements, considerable disturbing signal--respectively error--portions are measured, which, however, in practice are usually inaudible.
Simple frequency evaluations such as dB(A) do not take, in particular, masking effects into consideration. Ascertaining the "error signal" by means of elaborate frequency evaluations without taking the physiological sense of hearing into account or determining the THD factor (total harmonic distortion) does not give any distinct indication of the quality of the encoding algorithm so that hitherto encoding algorithms could only be evaluated by means of extensive hearing tests.
DESCRIPTION OF THE INVENTION
The object of the present invention is to provide an apparatus for checking audio signal processing systems, which will allow quantitative determination of the audibility of disturbing signals.
A solution, in accordance with the present invention, of the aforegoing object and its further embodiments are set forth in the claims hereto: an element of the present invention is that the apparatus is provided with a first input connection to which the input signal from the audio signal processing system to be checked is transmitted, a second input connection, to which the output signal of said system is transmitted, and a signal processor. The signal processor ascertains the signal delay time of the system to be checked by means of correlating the signals received at both input connections in such a manner that an "output signal" and the respective audio signal processed by the system to be checked are always compared.
In accordance with the embodiment described in claim 1 hereto, the signal processor always composes the difference signal from the signal received at the first input connection during a specific time span, by way of illustration approximately 10 ms, and the signal received at the second input connection, lagging by the signal delay time, and ascertains the spectral composition of the signal received during the specific time span at the first input connection and of its respective difference signal.
In accordance with the embodiment described in claim 2 hereto, the signal processor ascertains the spectral composition of the signal received during the specific time span (again, by way of illustration, approximately 10 ms) at the first input connection and of the signal received at the second input connection, lagging by the signal delay time, and always composes the difference signal of the spectral compositions of the signal received during the specific time span at the first input connection and of the signal received at the second input connection, lagging by the signal delay time.
In the case of both embodiments, the signal processor subsequently ascertains th
REFERENCES:
patent: 3786188 (1974-01-01), Allen
patent: 4548082 (1985-10-01), Engebretson
patent: 4577641 (1986-03-01), Hockmair et al.
patent: 4637402 (1987-01-01), Adelman
Walters, "Microprocessor Controlled Measurement System for Speech Codes", EE on Instrumentation and Measurement, Band IM-31, Nr. Mar. 1, 1982, pp. 12-17.
Brandenburg Karlheinz
Eberlein Ernst
Gerhauser Heinz
Kapust Rolf
Krageloh Stefan
Fraunhofer Gesellschaft zur Forderung der angewandten Forschung
Kemeny E. S.
LandOfFree
Apparatus for checking audio signal processing systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for checking audio signal processing systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for checking audio signal processing systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-945632