Frequency response testing apparatus

Claim 2

Frequency response testing apparatus comprising a generator for providing a first electrical signal of predetermined varying-frequency form representing an input for application to a device to be tested: a receiver for response to a second electrical signal representing the output of said device, said receiver including timing means connected to said generator to provide a plurality of sequentially occurring third electrical signals representing correspondingly occurring increments of said first signal; discriminating means responsive to said second signal for providing a plurality of fourth electrical signals respectively representing successively increasing amplitude levels therein; and a matrix of electrically-operable light-emitting elements, successive columns and rows of said elements being respectively operably responsive to corresponding ones of said third and fourth signals, and each of said elements being operable only in response to the simultaneous occurrence of the respective ones of said third and fourth signals.

Claim 3

Apparatus according to claim 1 comprising electroacoustic means connected to at least one of said generator and said receiver to operably couple said device between said generator and said receiver.

Claim 4

Apparatus according to claim 2 wherein said electroacoustic means comprise a loudspeaker connected to said generator, and a microphone connected to said receiver.

Claim 5

Apparatus according to claim 3 wherein said microphone is of miniature, hearing aid type, said microphone is mounted in the centre of a rigid baffle, said baffle is connected with an ear mould substitute, and said baffle and said ear mould substitute define therebetween the cavity of a 2 cm 3 coupler according to the international standard 1EC 126.

Claim 6

Apparatus according to claim 1 comprising a feedback circuit including an attenuator connected to said generator, and control means connected to said attenuator, said control means being operable in response to the output of said device to maintain, by way of said attenuator, the input to said device at constant amplitude.

Claim 7

Apparatus according to claim 5 wherein said feedback circuit comprises further electroacoustic means connected to at least one of said attenuator and said control means to operably couple said device with said circuit.

Claim 8

Apparatus according to claim 6 wherein said further electroacoustic means comprise a loudspeaker connected to said attenuator, and a microphone connected to said attenuator.

Claim 9

Apparatus according to claim 1 wherein: said generator comprises a ramp generator providing a sawtooth output signal, and a variable-frequency oscillator connected with said ramp generator to provide said first signal in response to said sawtooth signal; said timing means comprises a plurality of similar timing circuits, each including a trigger connected to said ramp generator to provide a respective one of said third signals in response to corresponding levels in said sawtooth signals, and a gate connected with said trigger to be opened for the duration of said one third signal; said discriminating means comprises a linear amplifier responsive to said second signal to rectify increments thereof of common amplitude, but varying frequencies, to corresponding DC levels, and a voltage-to-frequency converter having its input connected to said linear rectifier to provide said fourth signals, and having its output connected to said gate of each of said timing circuits for passage therethrough when open; and said matrix has successive ordinates connected to respective extensions of said timing circuits, which extensions each comprise a counter having its input connected with the respective gate for operation by the respective fourth signal, and its successive count outputs connected to successive elements of the respective ordinate of said matrix.

Claim 10

Apparatus according to claim 8 wherein said discriminating means comprises a logarithmic amplifier connected between said rectifier and said converter.

Claim 11

Apparatus according to claim 8 wherein the elements of said matrix comprise light-emitting diodes.

Claim 12

Frequency response testing apparatus comprising: a waveform generator for providing an electrical signal having a linearly increasing frequency, representative of an input for application to a device to be tested; means responsive to a signal indicative of the output signal of said device for generating a signal indicative of the amplitude of said device output signal; a matrix of electrically-operable light-emitting elements, interconnected in columns and rows; and means responsive to a signal indicative of said increasing frequency signal and said signal indicative of said device output signal, for selectively activating respective elements in said matrix disposed in columns in accordance with said frequency varying signal and rows in accordance with said tested device output signal amplitude, to provide thereby a display of the frequency response of said tested device.

Claim 13

Frequency response testing apparatus comprising: a waveform generator for providing an electrical signal having a linearly increasing frequency, representative of an input for application to a device to be tested; means responsive to a signal indicative of the output signal of said device for generating a signal indicative of the amplitude of said device output signal; a matrix of electrically-operable light-emitting elements, interconnected in columns and rows; and means responsive to a signal indicative of said increasing frequency signal and said signal indicative of said device output signal, for selectively activating respective elements in said matrix disposed in columns in accordance with said frequency varying signal and rows in accordance with said tested device output signal amplitude, to provide thereby a display of the frequency response of said tested device.