Acoustics – How To Soundproof a Room

Acoustics – How To Soundproof a Room


25 JANUARY 2017

written by Mike


How To Soundproof a Room


Acoustics is an art of measuring space and treating it with appropriate materials. Acoustic panels or acoustic foam are an easy example.

The minute you decide you want to pursue a career (or just a hobby) in sound and music, a question comes to a mind.

How to soundproof a room? Answer is:


The subject of acoustics is colossal and requires years of in-depth studying and experience. Try to think about it beyond soundproofing a room or recording studio. Soundproofing affects every underground metro station, every shopping mall, school or office. It is noise pollution, reverberation, and general ruckus that we are fighting.

City halls, churches, conference rooms. Architects design all these buildings with acoustics in mind.

If you want to get deeper into the subject, check

Architectural Acoustics by Marshall Long

This book is useful if you are serious about studying acoustics. It starts with a history of acoustics and human perception. But it also goes into a great detail of different kinds of buildings and designs. It is a heavy, around 800 pages volume. Not a bedtime read.

Why is it so rare to see an open-air orchestra? Or open-air opera?

One answer, there is no acoustics outside.

Ok, but what about these old theaters where people sat outside?

Yes, these places were (and still are) open air. Architects designed them with acoustics in mind too.

Music halls are exceptional in their design. These rooms must deliver the best sound possible. But, for example, think of hospitals.

How can soundproofing be important there?

We build hospital rooms with patients’ comfort in mind. Especially surgery rooms that need to minimalize outside distractions. To become an acoustician, you must learn physics of the sound, mathematical equations, computer programs and specialized measurement equipment. I want to introduce you to some basic concepts of acoustics. I will try to ignite in you a deeper interest in this subject.

I’m not going to lie; it is a bit of a challenge.



Measuring a room is not as easy as it sounds. The size of the room is important, but you also need to think about orientation and functionality of the place. And don’t forget about the volume of the room. Here comes the math.

The perfect solution would be to build the room from scratch. Rod Gervais writes how to transform room into a recording studio in

Home Recording Studio Build It Like the Pros, 2nd Edition

Great book for people, who are not as good in math or physics. Easy to understand text, full of pictures and easy to read graphs. And it goes step by step, from start to finish. There is a cool ‘acoustics myths’ chapter at the end too.

First thing that most people would do is to measure the frequency curve. It will show you what kind of acoustic treatment the room needs. For this task, you will need one of these weird looking microphones.



As critical as it is, think about other variables too. What is the isolation from the outside world? What about the spill from other rooms? How will the room be lit, powered and air-conditioned? Where are you going to put your desk? Also, the room will sound different with all the equipment inside.

So remember to take more just one measurement. Take a note of these few basic requirements that you will need to think about:

frequency balance, acoustic isolation, and separation, reverberation and cost.

Before committing to anything, do your research and analyze results of your measurements. Don’t rush it. There is a cool program that you can you use for your acoustic adventures called SketchUpI used it for my school acoustics projects. We designed a home recording studio with one of my colleagues. It is easy to use and fun. I suppose it is sort of like Sims.

Without actual Sims.


Treating a room is much more complicated that just putting some egg cartons on your ceiling and walls. And by the way, these are quite ineffective so do not waste your money or time on doing that. Acoustic treatment will make you think about the state of the doors, windows, walls and floor in your room.

How isolated are they?

Is it possible to enhance their effectiveness on a low budget?

It is also important to analyze frequency balance of space.

You will need to invest in some materials that will absorb, diffuse and trap the unwanted sound frequencies. Acoustic panels and acoustic foam are something to consider buying.

That’s where sound absorption coefficient charts come in handy

I know. These are fascinating to read.

The aim is to have frequencies balanced as much as possible. It means that whatever you mix in your room will sound good in other spaces. For small rooms like a bedroom, unwanted bass frequencies will pose the biggest threat. Do your research but making your bass traps can also be a great and a low-cost option to consider.




Reverberation is a big part of acoustics.

What is it?

Every time you make a sound (in a room) it reflects and bounces off walls, floor, and ceiling. You can have early or late reflections, depending on a journey of the sound. Imagine sitting in front of the speaker. 

The sound that hits you first is called direct signal. There is nothing between your ears and speaker’s cone that could block it. Beyond that, you have your sidewalls and maybe your ceiling. Some frequencies will reflect off these surfaces and then hit your ears. These are short reflections.

Late reflection is the sound that will travel to the wall at the end of the room and then travel back to you; you hear it after everything else.

How long can the sound bounce around like that?

Definition of reverb.

It is a period in which a sound diminishes to a millionth of its original intensity. You can calculate it with an RT60 equation of 60dB decrease over a certain time duration.

RT60 = Vx0.049/AS

V is the volume of the room

A stands for absorption coefficient of the room. That is the amount of acoustic energy absorbed rather that reflected

S is the total surface of the room

This formula can explain the reason sound lingers in a big cave.

You can calculate it here.

Accurate measurement of reverberation will help you to design your space for the best possible result. As you can see acoustics is a vast and deep subject. We haven’t even scratched the surface and already there are some equations to remember.


But consider this. If you want to build a small studio, space to record your online video channel or even just a home cinema, consider soundproofing your room. You will realize it is not as scary as it sounds.

Well, unless you want to design a concert hall or something.



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What is Sound?

What is Sound?


03 JANUARY 2017

written by Mike




The sound is a part of life. It is around you when you wake up; it is there when you go to sleep. Most of the animals communicate with sound. Humans use it to express their emotions, artistic creativity, and ideas.

A powerful speech, a roar of an engine in a sports car, chanting crowd during a big sports event. All kinds of sounds from quiet to deafening can have a big impact on us.

But what is sound?

Why things sound like they do?

Where does the sound come from?

And why should you care?

These questions puzzled people for millennia. But thanks to development in technology, now we can answer a lot of them.

Not all of them, though.

I want to give you a short introduction to the science behind the waveform, frequency and sound content. I hope it will inspire you to dig deeper into a wonderful world of sounds and noise.





We describe sounds as changes in atmospheric pressure.

Compressed air molecules cause the change to flow in the form of the wave through the atmosphere.

Molecules do not move with the wave. They only compress and decompress as the wave moves through a medium (air, water, and others) over time.

There is a difference when sound moves through water and air.

And because water is denser, sound travels much faster.

A waveform is a graphic representation of that journey.


Sound doesn’t look like this in real life.

But for now, don’t worry about it.

Waveform’s main characteristics are amplitude, frequency, velocity, wavelength, harmonic content and envelope.

Amplitude in the easiest. It is the loudness of the wave, the value from negative to positive peak.

Frequency is the rate of the vibrations in given time. Higher frequency equals higher pitch.

Velocity is the speed of sound. It is approximately 344 m/s (1120 ft/s) through the air at 20°C (68°F). The speed is temperature dependent, and when it gets hot the sound travels faster.

Wavelength is a physical distance between the start and the end of one wavelength cycle.

Harmonic content is the spectrum of frequencies called overtones.

Many frequencies create a sound, not just one.

Unless it is a single frequency sound.

The envelope is a characteristic variation that happens over time to played sound.

Envelope describes how quick sound makes a noise, how long it lasts and how fast it quiets downs.

What is up with Noises? (The Science and Mathematics of Sound, Frequency, and Pitch) is a great video that explains sound science in more detail.







Loudness is a general characteristic that we describe a sound as either loud or quiet.

But what is the measurement of loudness?

And what is the human threshold of withstanding loud sounds?

Do you remember last time when you went out to a live gig and the next day your ears were ringing?

Yes, it means it was too loud.

We measure loudness in the decibel or dB. There are a lot of variations, but the most common is sound pressure level SPL measured in decibels.

For example, a quiet conversation can be around 40dB, but a close up a jet engine is around 160dB.

Decibel is a logarithmic value that articulates differences in force between two levels. SPL is only one unit of measure, and there are much more such as voltage V and wattage W. It can get a bit complicated.

You can use SPL to describe loudness. It describes the built up of acoustic pressure in defined space, like a room.

Sound mixes in studios have the reference set between 79dB to 85dB.

The threshold of pain can start around 130 to 140dB.

Gunshots are around that barrier. That’s why you can see people wearing

noise-cancelling headphones at a gun range.

It is important that I mention human ear’s average sensitivity to different frequencies at various levels.

We describe this effect as Fletcher-Munson curve.

It is one of the studies that try to explain our perceptions of sound.

Our sensitivity to certain frequencies will make some sounds more dominant over the others. Even if they have the same loudness level.

For example, a 40Hz tone has to be about 6dB louder than a 1kHz tone at 110 dB SPL so you can perceive it with the same loudness.

We are more sensitive to sounds that are in a spectrum of a human voice.

The loudness can also deceive our perception of pitch.

Sounds with certain frequencies will overshadow other sounds. For that reason, EQ and frequency filtering are such a powerful tools when it comes to mixing.



Ok, so you need to hear a sound first. Sound pressure waves arrive at our ears where they journey as electric impulses to our brain.



The human ear has three basic parts, the outer ear, the middle ear and the inner ear.





The outer ear

gathers and transports sound to the middle ear. It includes Pinna (ear flap) and approximately 2cm long ear canal. It protects the middle ear from the damage and delivers sounds to the eardrum on the border with the middle ear.

The middle ear

transforms sound pressure energy into internal vibrations and compression wave. It contains an eardrum and three bones, the hammer, anvil and stirrup. Eardrum’s membrane sets off the bones. It transmits the vibrations to the fluid of the inner ear as a compression wave.

The human body is sensitive even to the most delicate sounds.

The frequency range of hearing is between 20Hz to 20000Hz.

Cats can detect frequencies as low as 45 Hz and as high as 85000Hz.

Any frequency below 20Hz we call an infrasound and anything above 20 000 is ultrasound.

The barriers to watch out for are the threshold of hearing, feeling, and pain.

The loudest sound possible is around 194dB.

But you will lose your hearing at 180dB!

Wear earplugs when working with loud sounds.

Even if you are going to a gig, some earplugs can make the music more enjoyable as you will hear it clearer.

And you won’t have to listen to drunken people singing around you.

A clear win-win.


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