Which of the following defines the frequency range of infrasound?
A: below 20 Hz20\text{ Hz}20 Hz B: between 20 Hz20\text{ Hz}20 Hz and 20 000 Hz20\,000\text{ Hz}20000 Hz C: above 20 000 Hz20\,000\text{ Hz}20000 Hz D: above 20 MHz20\text{ MHz}20 MHz
A musician plays a note on an electronic wind instrument, and a microphone connected to an oscilloscope is used to display the sound wave produced. The diagram shows the trace on the oscilloscope screen:
Calculate the frequency of this sound wave.
The musician then adjusts the instrument to produce a sound that is quieter and has a lower pitch. Describe how the amplitude and the horizontal wavelength of the trace on the oscilloscope would change, assuming the oscilloscope settings remain the same.
