How Is Pitch Measured?

Pitch, or frequency, is the measure of cycles per unit of time of a sound. It is a physical measurement. It is possible to measure pitch with great accuracy using electronic tools. It is also possible to measure pitch approximately by ear. Measuring pitch is important in such fields as music, music engineering, acoustics and psychoacoustics.

The unit most commonly used to measure pitch is Hertz. Hertz is a measure of cycles per second. Sound waves are oscillating phenomena in the air. A sound wave oscillates between high and low air pressure. A single cycle involves the wave reaching high pressure, dropping down to low pressure and reaching high pressure again. However many times a sound wave does this in a second is the number of cycles per second, and therefore the number of Hertz.

Scientists and engineers often use oscilloscopes to measure pitch. An oscilloscope is useful for looking at the waveform of a signal while measuring its pitch. An oscilloscope creates a graphical representation of a waveform. To use an oscilloscope to measure pitch, the user connects the signal to the oscilloscope using audio cables or a microphone. The user looks at the oscilloscope display and adjusts the knobs until the waveform is stationary. When the waveform is stationary, the user reads the settings of the controls, which indicate the frequency in Hertz.

A digital frequency counter is another way to measure pitch. A frequency counter calculates the input frequency and provides a numerical readout in Hertz. The user connects the counter in the same way as with the oscilloscope. When fed a stable pitch, the counter will indicate the pitch in Hertz. The advantage to using this method over the oscilloscope is that it provides a quicker result. The disadvantage is that the waveform is invisible.

The simplest but least accurate way to measure pitch is to do it by ear, using a musical instrument such as a piano. To measure pitch, the listener hears the sound which she wishes to measure, then plays the piano keys until she finds the key that most closely matches the pitch of the sound. The pitch of the sound is approximately the same as the name of the note. Or, the user can refer to a chart which gives the frequency for each note (see Resources).