What is sound?

Understanding what exactly sound waves are





Spaces are nothing without people in them.


When you’re designing a building, it’s important to consider some factors of comfort.

How will the occupants perceive it? What will the noise be like? How many people will occupy it?










But having more than one person in a room creates an acoustic problem: noise

If you have one person talking to itself, it won't bother no one.

But offices, for example, have a lot of people talking at the same time.

This creates unwanted noises, which can distract people and lower productivity.







Imagine a monkey banging cymbals.

When a monkey hits those cymbals together, they produce sound. That sound is produced because those cymbals vibrate. The vibrating sound source changes the particles around them. This changes the pressure in the air, creating areas of high and low pressure. These areas with different pressure are called sound waves, because they travel as waves of compressed air.








Those cymbals create sound waves that reach our ears

When sound waves reach our ears, the bones in our ear canal convert the vibrations into nerve impulses.
Then, they're interpreted by the brain.

At this point, we received the sound and interpreted it, and we recognize it as a “monkey banging cymbals”.








The way we perceive sound depends largely on two factors:





Frequency

Sound travels as waves of compressed air, and the distance between each wave can vary, depending on the source of the sound. The distance between sound waves is called the frequency.

The frequency is what determines the pitch of the sound and is measured in Hertz (Hz). For example: the normal talking frequency can be something around 200Hz, while a soprano can sing in ranges of 880Hz. But the human ear can hear frequencies from 20 to 20.000 Hz.

When you are trying to control human sound, it’s important you focus on the 200-1500hz frequency, so that voice is easily understood.

Sound pressure

Sound pressure is what can make us perceive sound as loud. The usual talking voice is something around 60 decibels, which is the measure of sound pressure. A truck passing by can produce sounds up to 100 decibels.

Note that making the sound pressure level 10 times higher is only a 10decibel increase. This means that decibels increase exponentially throughout their range.

Exposing yourself to sounds of 85db or more is hazardous, because they’re 25 times more intense than the normal talking voice.






Sound pressure and frequency can be perceived differently by different people.

A voice can be too loud for some or just right for others. A soprano singing can be disruptive for an opera attendant, while loud machines might be not so loud for a factory worker.

Loudness is a subjective measure, and everyone perceives it differently.












Next: how does sound behave inside a room?