Sound Vs Noise - Are they the same?

Sound? or noise?

These two terms – “sound” and “noise”, are very commonly used in our daily conversations. For example, when a group of people are talking loudly, we say “They are making a lot of noise.”. Or when heavy metal music starts to blast from the loudspeaker, we say “That is a loud sound coming out from the speaker!”.

But are we using them correctly? Do they mean the same thing?

No.

Image by Gerd Altmann from Pixabay
Image by Gerd Altmann from Pixabay

To be clear, they are related, but not the same. Here is a quick tip on how to differentiate them: Noise is sound, but sound is not noise. Here’s why:

Sound can be defined as a form of energy transmitted by pressure variations (DOSH, 2016). In physics terminology, sound is also a vibration formed by an acoustic wave propagation, going through a transmission medium (e.g. solid, liquid or gas). It occurs when air particles undergo vibration, generating pressure waves in the air. In layman’s terms, sound is basically what you hear.

What about noise?

Noise is actually an unwanted sound (DOSH, 2016). When noise gets too loud, it causes unpleasantness, distraction, distress, or sometimes even permanent hearing damage. This damage is strongly reliant on a few factors, including volume (loudness), frequency (pitch) and the exposure time to loud noise. Now, slightly turn down your speaker volume, and listen to the noise track below to get a clearer “picture” about noise:

Not very pleasant, is it?

Measurement of sound

Just a quick overview about sound measurements, sound measurement can be done in the form of loudness and its pitch. Loudness of sound is usually measured in decibels (dB), which shows the energy level of the pressure wave (Rose, 2002). The pitch, however, is measured in the form of frequency, which has the unit Hertz (Hz) (Pilhofer, 2007). A higher frequency means higher pitch, and the same applies for loudness in decibels.

Typically, the human ear can pick up sound frequencies between the range of 20 Hz to 20 kHz, whereby it is most sensitive at 500 Hz to 4 kHz, falling between the speech range of humans (Olson, 1967).

Try listening to the tones below to get an idea about the difference between a 500 Hz pitch and 4 kHz pitch. (Warning: KEEP YOUR VOLUME LOW!)

Did you hear the difference? The higher frequency (4 kHz) sounds a lot more piercing as compared to the lower frequency sound (500 Hz).

This article is generally a brief overview about the basis of acoustics, which of course includes sound. Once you are ready, join us to dive deeper into the world of acoustics!

References

DOSH, D. O. O. S. A. H. M., 2016. Introduction of Noise and Legal Requirements

Olson, H. F., 1967. Music, Physics and Engineering. Dover Publications.

Pilhofer, M., 2007. Music Theory for Dummies. 

Rose, J., 2002. Audio postproduction for digital video. p. 25.

Written by Khei Yinn Seow

Posted on August 7, 2020

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