Nico Valentinus Franssen

Direction and frequency independent column of electro-acoustic transducers

An electro-acoustic arrangement comprising a plurality of transducer units including five, seven or nine equally spaced transducers situated in line with the transducers connected to a transmission channel via individual amplitude control devices. The amplitude control devices are adjusted so that the ratios between the conversion factors of the transducer units viewed from end to end are 1:2n:2n2 :-2n:1 for five transducers to produce an output signal substantially independent of direction and/or frequency. The invention also relates to a combination of five, seven or nine of the foregoing arrangements situated adjacent each other or in line at equal distances with further amplitude control devices connected to a transmission channel. The amplitude control devices are adjusted so that the ratios between the conversion factors of the arrangements, viewed from end to end, form a special relationship.

Artificial reverberation apparatus for audio frequency signals

An artificial reverberation apparatus for audio frequency signals, comprises a first delay device preceded by an adder. A feedback circuit couples the output of the delay device to an input of the adder to give a loop signal gain of less than unity. The adder is preceded by a second delay device with the same delay time as said first-mentioned delay device. The signal to be delayed is applied to the input of said second delay device and also to the adder via a transmission path. The ratio of the signal gain of the transmission path to the signal gain of said second delay device is equal to but of opposite sign to said loop signal gain. Preferably the signal gain of the transmission path is equal to but of opposite sign to the signal gain of said feedback circuit. Furthermore, a plurality of apparatuses can be connected in cascade with the delay devices of the different apparatuses all having different delays.