Pitch and frequency relationship

pitch and frequency relationship

From Wikipedia - Pitch (music) > Frequency is an objective, scientific attribute that can be measured. Pitch is each person's subjective perception of a sound. A high pitch sound corresponds to a high frequency sound wave and a low pitch sound corresponds to a low frequency sound wave. Amazingly. There is a relationship between pitch and frequency. The faster the vi- bration of something producing a sound, the higher the pitch we tend to perceive that.

Hz is an abbreviation of the unit Hertz, named after the physicists Heinrich Hertz. Once we understand the meaning of a pitch or frequency of Hz, we can ask a related question: Another way to look at this is the following: Again, we have used some shorthand notation. If the period is rather small, we don't want to keep writing lots of zeros after the decimal point, so we use scientific notation, instead. This is especially convenient for sound waves, as the periods of sound waves are generally around 1 to msec.

Consider the Earth going around the sun. Is this motion repetitive? What would an oscillation correspond to? What is the period and frequency of the motion? What is the period and frequency of the wave on the following graph? Repetitive sounds can be formed in different ways.

pitch and frequency relationship

The most common, of course, is from a musical instrument. But, now, consider the situation where you are standing in front of a set of bleachers and you strike a bass drum: The individual echoes of the drum off each step are delayed from one another.

Pitch and Frequency

So, to the drummer the echoes form a repetitive sound which then is heard as a pitch. Anyone who has played in a marching band can attest to this!

Frequency and Pitch of Sound

Amplitude - Loudness Besides the pitch of a musical note, perhaps the most noticeable feature in how loud the note is. The loudness of a sound wave is determined from its amplitude.

While loudness is only associated with sound waves, all types of waves have an amplitude. Many things can influence the amplitude. What is producing the sound?

How far are you from the source of the sound? The farther away the smaller the amplitude.

pitch and frequency relationship

Sound does not travel through walls as well as air. Depends on what is detecting the wave sound. The Human Ear A sound wave, like any other wave, is introduced into a medium by a vibrating object. The vibrating object is the source of the disturbance that moves through the medium. The vibrating object that creates the disturbance could be the vocal cords of a person, the vibrating string and sound board of a guitar or violin, the vibrating tines of a tuning fork, or the vibrating diaphragm of a radio speaker.

Regardless of what vibrating object is creating the sound wave, the particles of the medium through which the sound moves is vibrating in a back and forth motion at a given frequency.

The frequency of a wave refers to how often the particles of the medium vibrate when a wave passes through the medium. The frequency of a wave is measured as the number of complete back-and-forth vibrations of a particle of the medium per unit of time. If a particle of air undergoes longitudinal vibrations in 2 seconds, then the frequency of the wave would be vibrations per second.

This is sensible since each particle vibrates due to the motion of its nearest neighbor. The first particle of the medium begins vibrating, at say Hz, and begins to set the second particle into vibrational motion at the same frequency of Hz. The second particle begins vibrating at Hz and thus sets the third particle of the medium into vibrational motion at Hz.

The process continues throughout the medium; each particle vibrates at the same frequency.

pitch and frequency relationship

And of course the frequency at which each particle vibrates is the same as the frequency of the original source of the sound wave.

Subsequently, a guitar string vibrating at Hz will set the air particles in the room vibrating at the same frequency of Hz, which carries a sound signal to the ear of a listener, which is detected as a Hz sound wave.

The back-and-forth vibrational motion of the particles of the medium would not be the only observable phenomenon occurring at a given frequency.

Pitch and Frequency

Since a sound wave is a pressure wavea detector could be used to detect oscillations in pressure from a high pressure to a low pressure and back to a high pressure. As the compressions high pressure and rarefactions low pressure move through the medium, they would reach the detector at a given frequency.

For example, a compression would reach the detector times per second if the frequency of the wave were Hz. Similarly, a rarefaction would reach the detector times per second if the frequency of the wave were Hz.


The frequency of a sound wave not only refers to the number of back-and-forth vibrations of the particles per unit of time, but also refers to the number of compressions or rarefactions that pass a given point per unit of time.

A detector could be used to detect the frequency of these pressure oscillations over a given period of time. The typical output provided by such a detector is a pressure-time plot as shown below.

pitch and frequency relationship

Since a pressure-time plot shows the fluctuations in pressure over time, the period of the sound wave can be found by measuring the time between successive high pressure points corresponding to the compressions or the time between successive low pressure points corresponding to the rarefactions. As discussed in an earlier unitthe frequency is simply the reciprocal of the period.