When you change the transmit frequency which of the following is altered?

• A. Displacement amplitude of the particles in the medium.
• B. Speed at which the sound wave propagates through the medium.
• C. Number of cycles per second.
• D. Pulses transmitted per second.

Answer: (C)

The key idea is that frequency is the rate at which the wave oscillates, measured in cycles per second (Hz). When you adjust the transmit frequency, you are changing how many cycles occur each second, so the number of cycles per second changes accordingly. The speed at which the sound travels through the medium depends mainly on the medium’s properties and stays essentially the same for a given medium (aside from minor dispersion effects). The displacement amplitude of the particles depends on how much energy you drive into the wave, not on how quickly it oscillates. Pulses transmitted per second (the pulse repetition frequency) is a separate parameter that governs how often bursts are sent and isn’t tied to the carrier frequency. So, changing the transmit frequency alters the number of cycles per second.