The Main Characteristics Of Sound

By Antonia Čirjak on June 16 2020 in Science

Sounds you hear every day, and even those you can not detect, behave like waves.
Sounds you hear every day, and even those you can not detect, behave like waves.
  • The loudness of a sound is measured in decibels (dB). A fighter jet taking off will achieve a loudness of around 150 dB if you are around 80 feet away from it. Please do not do that, as it will most certainly rupture your ear.
  • A cat’s ultrasound range detection is much higher than ours, and they can detect frequencies all the way up to 85,000 Hz.
  • If something is vibrating 1000 times per second, it means that it has a frequency of 1 kHz (1000 Hz).

Sounds you hear every day, and even those you can not detect, behave like waves. Waves can appear in nature on and in between many different types of matter. There are waves that move the sea, the waves you see as the wind blows into your curtain, or that highly acrophobic realization that you can see an 820-foot tall tower moving left and right if you stand right on top of it. 

I’m Pickin’ Up Good Vibrations

All matter can move, and we do not have to climb up a tower to realize that. The sounds that reach your brain are soundwaves that traveled through the air because objects have one crucial ability - they can vibrate. Matter and objects around us can vibrate because they react to different forces affecting them. 

Technically speaking, it is the fact that the molecules of any given material can juggle around is what helps them retain their solidity. Imagine if there was an earthquake, and the material your house was built has no ability to respond to vibrations with vibrations. It would be too rigid and be prone to collapsing because there is no flexibility. Now, how is all of this connected with sound?

Frequency

First of all, when we talk about vibrations, we are talking about frequency. This value is expressed in Hertz (Hz). A Hertz tells us how fast an object is vibrating, and therefore, what is the frequency of the sound. 1 Hz means that the soundwave completes one full cycle within one sound. So frequency = vibrations per second. 

Audio sound frequency spectrum
Audio sound frequency spectrum.

For example, the low A note on a bass guitar, once you slap it, vibrates in the frequency of 110 Hz, if your bass is tuned right. If you strum the open A string on a guitar, it will have a frequency of 440 Hz. Bear in mind, this is still the same note - both are achieving the same pitch, but just in different octaves. That is why we can talk in terms of high and low frequencies: the A note on a bass guitar has a lower frequency than an A note on an acoustic guitar. This is a property of all sounds - all of them can achieve a specific pitch. 

Range

Humans, for example, differ from other species in the ability to hear a limited range of frequencies. A perfectly healthy human can hear frequencies from 20 to 20,000 Hz. Bats can hear everything from 20 to 120,000 Hz, which is why they are so good in echolocation they use for navigation. But, hear this, dolphins have a range of 0,25 to 200,000 Hz! That is impressive on so many levels because they are capable of hearing both infrasound and ultrasound frequencies exceptionally well.

We can not perceive infrasound, the one that goes below 20 Hz. This does not mean those sounds do not exist in our environment, but most of the sounds you hear that are below 40 or 50 Hz come mostly to a feel thing. Imagine standing in front of a sub-bass speaker. Those can technically produce frequencies below our hearing range, but you can still feel them, mostly as a very deep ‘’thump’’ in your chest. However, some species, like dolphins, can even communicate on an ultrasonic level, above 20,000 Hz.  

Loudness 

The final distinguishable feature of every sound is its loudness. This is different from the pitch in a way that it is not the frequency that is changing, but only the amplitude. The higher the amplitude is, the louder the sound will become. Let us check some examples. 

First, when you are listening to your radio, or music in your headphones, the speakers that are transmitting the sound to your ears are vibrating. As your favorite song comes next, you turn up the volume. By doing that, you turn up the loudness. Now, there is more energy pushing those same speakers, and the molecules of air that are constantly being pushed towards you, now do the same thing, but faster. The same goes if we pick that same A string on a bass: do it lightly, and it produces a softer sound, pick it hard, and it will become much louder. The energy you applied with your hand is stronger, which means that there is more force to move the string and increase the amplitude.

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