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== pulsing audio ==Ultrasonic sound diminishes rapidly over distance. You will have to drive the piezoelectric tweeter with sufficient voltage to generate a loud enough sound that it remains effective over the distance between the cannon and the neighbor's dog. However, you can destroy the piezoelectric tweeter if too much power is applied. To help mitigate damage to the piezoelectric tweeter it is suggested you provide the audio voltage in pulses rather than as a constant. * amplified audio pulses above 20kHz