Frequency is one of the most important concepts in sound. It is the basic building blocks of sound engineering – the alphabets of sound.

In this article, we’ll explore what is frequencies and what it means for sound waves to have different frequencies, and how frequencies are related to our perception of music.

What is Frequency?

Sound waves are generated by vibrations in the air or other media like water or solids.

The simplest example of a sound wave is a sine wave, shown above.

Sound waves move in cycles. One cycle will have one peak and one trough.

Frequency is the number of cycles that a wave completes in one second.

What is Hertz?

The unit of measurement for frequencies is Hertz (Hz) or number of cycles per second. It measures the number of times a wave repeats itself in one second.

If a sound wave repeats itself one time each second, it would have a frequency of 1 Hz.

If a sound wave repeats itself 30 times every second, its frequency would be 30 Hz.

Listen to a 30 Hz sine wave. You will have to listen very closely because it a very low frequency and will sound more like a rumble. If you are using headphones, keep the volume low to avoid hearing damage.

If a sound wave repeats itself 80 times a second, it would be a 80 Hz sound wave.

Listen to a 80 Hz sine wave. If you are using headphones, keep the volume low to avoid hearing damage.

Once the frequency gets to 1,000 Hz, it often shorted with the letter “k”. For example, 1000 Hz is the same as 1 kHz.

Listen to a 1 kHz sine wave. If you are using headphones, keep the volume low to avoid hearing damage.

5,600 Hz would be 5.6 kHz.

Listen to a 5.6 kHz sine wave. If you are using headphones, keep the volume low to avoid hearing damage.

Frequencies that Humans can Hear

The human ear can can hear frequencies that are between 20 Hz and 20,000 Hz (20 kHz ). Anything that is below 20 Hz or above 20 kHz is inaudible to humans.

It should also be noted that as a person grows older, he or she will start to lose his or her ability to hear higher frequency sounds.

How Do Frequencies Relate to Music?

Frequency is closely related to pitch. Higher frequency sounds are higher pitched. A super-shrill sound like a whistle has a very high frequency.

On the other hand, low frequency sounds can come across as more rumbly and deep sounding.

Musical notes are tied to specific frequencies. One frequency that musicians would be familiar with is A440. This is often used as a standard reference point for instruments to tune to. It is the pitch of of the musical note A above Middle C and has a frequency of 440 Hz.

Listen to a 440 kHz sine wave. If you are using headphones, keep the volume low to avoid hearing damage.

Other musical notes have different frequencies. The frequency of Middle C on a 88-key piano is 262 Hz. The lowest note on the piano is an A and has a frequency of 27 Hz. The highest note on the piano is a C and has a frequency of 4186 Hz.

Measuring Frequency

If you have a digital tuner or have spectrum analyzer downloaded onto your smart phone, you can view the frequencies visually.

Summary

Frequency is the number of complete cycles per second a sound wave makes. It’s measured in Hertz (Hz).

Frequency is closely related to pitch, because human ears can perceive certain frequencies as being higher or lower than others.

Next, you can learn about amplitude.

What is Sound?

Sound is a created by the vibrations of molecules in the air, water or solids. When these vibrations reach your ear, they’re converted into electrical impulses by your ear drum. Your brain then interprets these electrical impulses as sound.

Sound is Energy

These vibrations can originate from various sources. These include the human vocal cords (which comes out as vocal sounds or words) or things being hit together, for example hands clapping.

Musical instruments can be another source of these vibrations and different musical instruments used different means to create the vibrations. For example, a saxophone has a reed that vibrates and moves the column of air in the saxophone. A drum generates sound waves when it is hit.

Energy is required to start all these vibrations, whether by clapping hands or blowing into a saxophone. This energy then gets transmitted through media like air, water or solids to the ear. This is why you will also hear people refer to sound as energy.

Sound Waves

Sound waves refers to how sound travels.

When you look at waves in the ocean, you can observe them rising and falling traveling as they towards the shore. The waves rise up to peaks and then fall to troughs as they move along.

Similarly, you can observe a caterpillar moving in waves by bunching up its body and then extending it in order to advance forward.

Sound waves are how sound energy travels from the source (e.g. hands clapping) to the destination (e.g. the ears).

Peaks & Troughs

Sound waves belong to a family of waves known as longitudinal waves. in a longitudinal wave, the movement is along the same direction as a wave.

Imagine a slinky toy. There are two ways that you can create waves using a slinky.

The first way is to shake it up and down. This results in a wave where you can see a visible hump along the slinky. This is known as a transverse wave.

The second way to create a wave with a slinky is to hold one end stationary while moving the other end back and forth in the direction of the stationary end. You won’t see a visible hump but there are waves created as parts of the slinky get squeezed and stretched.

Sound waves are similar to the second type of wave known as longitudinal waves. The characteristic of the longitudinal wave is that the wave pattern moves in the same direction as where the wave is going.

Visualizing Sound Waves

Sound waves can be visualized by plotting out where the air molecules are squeezed and stretched. The technical term for molecules being squeezed together is compression (i.e. the molecules are being compressed together) and when they are stretched apart, this is know as rarefaction.

By plotting out where the compressions and rarefactions are on a graph, you will get a visualization of the sound wave.

The peaks are where the molecules are compressed together and the troughs are where they are stretched apart.

Conclusion

So, now that you know all this, the next time you hear a noise, think about what it really is — the vibration of molecules traveling through the air to reach your ear.

Next: Learn about frequencies

Maybe you’ve been told to take over the management of the sound at a venue, or are setting up a new sound and AV support team. But what exactly does that entail and what do you need to do? In other words, what exactly are the responsibilities of a sound operator or sound engineer, especially in a live sound setting?

Overview of What a Sound Engineer / Sound Operator Does

The sound engineer is responsible for operating and maintaining the sound equipment. This is true whether it is for live performances or in a studio. This involves setting up, adjusting, and managing the sound system, as well as troubleshooting and resolving any sound issues that may arise during a performance.

However, the responsibilities of a sound operator also goes beyond just the equipment aspect. It also involves human interactions and there are people skills required too. This last one is very often undiscussed and under-appreciated aspect of the role.

The responsibilities of a sound engineer or sound operator include:

Being sympathetic to what is happening on stage

A sound operator is not just a member of the behind the scenes crew but an essential part of the action that is taking place on stage. Therefore, an essential quality is that the sound operator must be aware of and sympathetic to what is going on on stage. This could be understanding how a band wishes to sound, or wanting to help a presenter on stage deliver his or her message across to the audience as audibly clearly as possible.

Setting up and configuring the sound system

This includes setting up the speakers, amplifiers, mixing console, microphones, and other equipment to make sure it is in proper order to be used.

Soundcheck

Running a soundcheck is the process of setting the levels and adjusting the processing of the sound, for example equalization of the different instruments and vocals in the mix. This is to ensure that all elements are balanced and that the overall sound is clear and pleasing.

Mixing the sound

During a performance, the sound engineer is responsible for adjusting the levels, equalization, and other settings of the sound system to achieve the desired sound.

Troubleshooting sound issues

A good sound operator will be able to quickly identify any sound issues that may arise during a performance. It is then his or her responsiblity to make sure that the issue is addressed as quickly as possible.

Maintaining the sound system

The sound engineer is responsible for keeping the sound equipment in good working condition. In a venue, this may mean regular maintenance which could require him or her to call in the right technicians to make necessary repairs or replacements.

Working with other members of the production team

Sound engineers often work closely with other members of the production team. These include crew like the lighting designer and the stage manager. By working together, the sound engineer can help to make sure that the overall production runs smoothly.

Keeping up to date with new developments and technology

Like many other areas of work, the field of sound engineering that is constantly evolving with new technology. It is important for sound engineers to stay up to date with the latest equipment and techniques.

These are some of the main responsibilities of a sound engineer or sound operator that is managing sound systems. Depending on the venue, event or the company they work for, the duties might vary. The role of sound engineer is a crucial one as it can make or break the overall experience of the audience.

Next: Learn about what is sound and sound waves.