Submarine propeller cavitation noise simulator

Claim 2

Apparatus for generating signals simulative of propeller cavitation noise from a source of first analog signals representative of water pressure P, a source of second analog signals representative of blade rate, and a source of band limited noise signals, said apparatus comprising: first means for converting said first analog signals to a first frequency which is proportional to the square root of P; second means for converting said second analog signals to a second frequency which is proportional to blade rate; third means for periodically providing an output which is directly proportional to said blade rate and inversely proportional to the square root of P in response to said first and second frequencies; fourth means for modulating said noise signals to provide pulses thereof at said blade rate and having a pulse width which is a function of said output of said third means; and fifth means for attenuating said pulses in amplitude by an amount which is a predetermined function of said output of said third means.

Claim 3

Apparatus as defined in claim 1, and wherein: said first means comprises first voltage to frequency converter means; said second means comprises second voltage to frequency converter means; said third means comprises counter means for providing a count in binary form of input pulses at said first frequency, first gate means for reading out said count, hold circuit means for holding said count after read out until a new count is developed, first and second delay means for effecting read out of each new count after resetting of said hold circuit and before resetting of said counter means; and said fifth means comprising one-of-N decoder means for rendering a condition change at a predetermined one of N output connections of said decoder means corresponding to each count read out of said counter means, a plurality of attenuator elements, a plurality of electronic switching means each being responsive to a change of condition at one of said connections to connect a corresponding one of said attenuator elements in series with said fourth means.

Claim 4

Apparatus as defined in claim 2, and wherein: said fourth means comprises third voltage to frequency converter means for converting said second analog signals to a series of pulses at said blade rate, function generator means for providing a voltage which is a predetermined function of the output of said third means, voltage variable pulse width one-shot means for rendering a train of pulses at said blade rate and having widths determined by the output of said function generator means, and second gate means for passing said noise signals to said electronic switching means.

Claim 5

Apparatus as defined in claim 3, and wherein: said attenuator means comprises at least one additional attenuator element and at least one additional electronic switching means Responsive to condition change at one of said decoder output connections to connect said additional attenuator element directly in series with said source of noise signals.