US 4,628,530 A · Automatic equalizing system with DFT and FFT

Abstract

The equalizing arrangement in accordance with the invention comprises an equalizing unit (4) for correcting the frequency characteristic of an electric signal applied to its first input (7) under the influence of a control signal (10) applied to its second input (8) and for supplying a corrected electric signal to its output (9), and a frequency analyzing unit (16) having a first input (15) coupled to a point in the signal path between the input terminal (1) and the first input (7) of the equalizing unit (4), a second input (17) coupled to the pick-up means (14) and an output (19) for supplying the control signal (10). The analyzing unit (16) is constructed to apply a Fourier transform to the previously digitized input signals x(t) and y(t) applied to its first and its second input, to compute Fourier-transformed signals F.sub.x (f) and F.sub.y (f) of these two signals and to compute a transfer function between these two signals. Preferably the frequency analyzing unit is further constructed to compute a coherence function .gamma..sup.2.sub.xy (f) between the two signals and, in determining the control signal, to ignore the values of the transfer function for those frequencies f.sub.i for which .gamma..sup.2.sub.xy is smaller than a specific value, for example 0.8. By means of the arrangement in accordance with the invention a better equalization can be achived and the distortion of the output signal of the arrangement is low.

Claims11

Dependent claims

An arrangement for converting an electric signal into an acoustic signal, which arrangement comprises:

an input terminal for receiving an electric input signal,
an electro-acoustic transducer unit for converting an electric signal into an acoustic output signal,
an equalizing unit having a first and a second input and an output, for correcting the frequency characteristic of said electric input signal, which is applied to its first input, under control of a control signal applied to its second input and for supplying the corrected electric signal on its output to said tranducer unit,
pick-up means for detecting an acoustic signal and for generating an electric feedback signal which is a measure of the acoustic signal, and
a frequency analyzing unit having a first input coupled to a point in the signal path between the input terminal and the first input of the equalizing unit, having a second input coupled to the pick-up means, and an output for supplying the control signal, which output is coupled to the second input of the equalizing unit, the improvement wherein analog/digital converter means convert said electric input signal and said feedback signal to respective digital signals, the frequency analyzing unit is constructed to subject the previously digitized digital input and feedback signals respectively applied to its first and second input to a Fourier transform, to provide Fourier-transformed versions F.sub.x (f) and F.sub.y (f) respectively of said signals, to calculate a transfer function from the said two versions, and to determine the control signal using the information in this transfer function.

2 more elements

Dependencies are inferred from the claim text.

Automatic equalizing system with DFT and FFT

Life of this patent

Automatic equalizing system with DFT and FFT

Life of this patent

Abstract

Claims11