What is Hertz Frequency: The Science Behind Sound Waves

Sound waves are amongst the most fascinating aspects of Physics, and borrowing from the famous saying, what we do not know about sound waves is more than what we know. Every sound we hear has a unique signature, the sum total of all the waves that created it. Frequencies are essential when it comes to sound waves, and hertz is one of the units of frequency. In this article, we will explore what hertz frequency is and the science behind sound waves.

What is Frequency?

Frequency is the number of times a wave oscillates in a second, and it is measured in hertz (Hz). When it comes to sound waves, frequency corresponds to the pitch of the sound we hear. Higher frequencies correspond to higher pitches, and vice versa. In other words, frequency is the number of cycles or vibrations the wave completes in a given time, which is usually one second. Since sound waves are often periodic, engineers and scientists use the term “cycles per second” instead of frequency.

Hertz as a Unit of Frequency

The unit “hertz” is named after Heinrich Rudolf Hertz, who is best known for showing that electromagnetic waves could be transmitted through air or a vacuum. 1 Hz is equivalent to one cycle per second. Humans can typically hear frequencies between 20 Hz and 20,000 Hz, and sounds outside of this range are usually not audible to us.

How are Sound Waves Created?

Sound waves are created when there is a disturbance in the air or a medium around us. The disturbance causes molecules or particles in the medium to move, creating a wave that moves through the medium. When the sound wave reaches our ears, it causes our eardrums to vibrate, sending electrical signals to our brain that we interpret as sound.

The Science Behind Sound Waves

Sound waves can be described using two fundamental concepts, which are amplitude and frequency. Amplitude is the measure of the energy levels within a wave, and it is usually referred to as loudness when discussing sound waves. Frequency, on the other hand, is a measure of how quickly the wave oscillates or cycles. A sound wave with a high frequency has a high pitch, and a sound wave with a low frequency has a low pitch.

Another critical aspect of sound waves is the speed at which they travel. They move through air at a speed of approximately 343 meters per second at room temperature. This speed is much faster in denser media such as liquids and solids. The speed of sound in water, for example, is about 1,500 meters per second.

Hertz and Musical Notes

Music is often composed of multiple sounds, which are a combination of various frequencies. Musicians use scales to classify these frequencies based on their pitches. One of the most commonly used scales in Western music is the chromatic scale, which divides an octave into twelve equal parts. Each frequency corresponds to a different note in the scale. Hertz frequency is used to describe the frequencies of musical notes, and it is used extensively by musicians and sound engineers.

Calculating Musical Frequencies

To calculate the frequency of a note, you can use the formula f = 440 x 2^(n/12), where f is the frequency of the note, n is the number of semitones above or below A4, and 440 is the frequency of A4. For example, the frequency of C5 can be calculated as follows: n = 3, f = 440 x 2^(3/12) = 523.25 Hz. C5 is one of the notes found in the C Major scale.

Hertz and Electromagnetic Waves

Hertz is also used as a unit of frequency for electromagnetic waves, including radio waves, microwaves, and visible light. Electromagnetic waves are created by the oscillation of charged particles, and they do not require a medium to travel through. Radio waves, for example, are used for communication, while visible light is responsible for the colors we see.

Electromagnetic Radiation Spectrum

The electromagnetic radiation spectrum can be classified based on frequency, wavelength, or energy levels. Both frequency and wavelength are inversely proportional, meaning that higher-frequency waves have shorter wavelengths, and vice versa. Visible light, which is composed of seven colors, is only a small part of the electromagnetic spectrum. From the highest frequency to the lowest, the electromagnetic spectrum is divided into several categories: gamma rays, X-rays, ultraviolet radiation, visible light, infrared radiation, microwaves, and radio waves.


In conclusion, frequency is the number of cycles or vibrations a wave completes in a second, and hertz is a unit of frequency. Sound waves are created when there is a disturbance in the air or a medium around us, and they can be described using amplitude, frequency, and speed. Hertz frequency is used to describe the frequencies of musical notes, and it is also used as a unit of frequency for electromagnetic waves. Understanding hertz frequency is essential in various fields and can help us understand the world around us better.

Common Questions and Answers

  • What is a hertz?
    • Hertz is a unit of frequency that measures the number of cycles or vibrations of a wave in a second.
  • What is the relationship between frequency and pitch?
    • Frequency and pitch are directly proportional, meaning that a higher frequency corresponds to a higher pitch.
  • What is the speed of sound, and how does it change in different media?
    • The speed of sound is about 343 meters per second at room temperature, and it increases as the medium becomes denser.
  • How are musical notes and frequencies related to each other?
    • Musical notes are different frequencies that correspond to different pitches. Hertz frequency is used to describe the frequencies of these notes.
  • What is the electromagnetic spectrum?
    • The electromagnetic spectrum is the range of frequencies of electromagnetic radiation, and it is divided into categories based on frequency, wavelength, or energy levels.


  • University Physics, Young and Freedman, 13th Edition, pp. 541-570
  • Introduction to Electrodynamics, Griffiths, 3rd Edition, pp. 51-55
  • Music Theory for Computer Musicians, Hewitt, 1st Edition, pp. 1-20

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