Conversion of acoustic signals into visual signals

In apparatus for converting acoustic signals into visual signals and including a plurality of parallel connected frequency filters connected to receive the acoustic signals and divide them into selected frequency bands, and a cathode-ray tube having a luminescent screen on which the divided acoustic signals are made visible by controlling the brightness of the cathode-ray beam as a function of the intensity of the signals from the filters, the improvement wherein there are three said filters each of which is a bandpass filter having a triangular amplitude versus frequency transmission characteristic and said filters comprise a three-channel filter device each channel of which has a pass-band extending over a respectively different frequency range such that the frequency ranges of adjacent pass-bands partially overlap one another, and each channel of which is provided with a respective output for providing a rectified signal, and said apparatus further comprises:

• a modulator device connected to furnish a rectified signal having an amplitude which corresponds, at every point in time, to the audio level of the acoustic signals applied to said filters;
• an image storage device presenting three image storage channels each having a first input, a second input and an output providing a signal representative of the signals at its inputs, the first input of each said storage channel being connected to receive the rectified signal furnished by said modulator device and the second input of each said storage channel being connected to the output of a respective filter device channel;
• and a color television monitor including a cathode-ray tube having three color signal inputs each connected to be controlled by the signal at the output of a respective storage channel.