Asound mixer is impressed by the new equipment that was just installed in his recording studio. he says that now he will be able to singers and musicians produce better cds because he can eliminate unneeded and undesired wavelengths. what term describes the characteristic of sounds waves that the sound mixer is now able to alter?

The answer is "Frequency".

Frequency is the speed of the vibration, and this decides the pitch of the sound. It is just valuable or important for melodic sounds, where there is a firmly consistent waveform. Frequency  is estimated as the quantity of wave cycles that happen in one moment. The unit of Frequency estimation is Hertz (Hz for short).  

A Frequency of 1 Hz implies one wave cycle for each second. A Frequency of 10 Hz implies ten wave cycles for every second, where the cycles are significantly shorter and closer together.