Why You Need to Pay Attention to Your Room Acoustics and Basics About Sound

With the availability of more compact and less expensive recording gear, available and easy to use software, it becomes very easy to record your gigs at home. 

But despite the fact this gear has definitely become much better, there is a limitation on home voice over recordings.  Most professional magazines talk about latest and most sensitive microphones or software that allows to “filter” the noise and “make you sound better”, yet it still does not sound as good as a recording made in a “professional” recording studio.

The reason is acoustics.  If your room does not sound good – it will be very difficult to produce great sounding results.  This, of course, translates to your ability to get repeat business and eventually make a good living doing what you love.

Acoustics can get intimidatingly complex, but treating tour room acoustically does not have to be difficult, or require hours in front of a calculator. Understanding how sound works in the room and how to apply that to creating your home recording space can get you a long way to sounding your best without major construction work or spending too much money.

Whether you are converting your garage, bedroom or a closet into your voice over recording studio, knowing the basic principles of how the sound works will help you to improve the sound in the room you are making the recording.


Acoustics is defined as

  • the science that deals with the production, control, transmission, reception, and effects of sound and
  • the qualities or characteristics of a room, auditorium, stadium, etc., that determine the audibility or fidelity of sounds in it.


In most cases improving the acoustics in your room will result in the biggest improvement in the way your recording sounds.

So while the expensive microphones allow you to capture your best sound, it is the room acoustics is what allows you to sound your best.

This is why commercial studios spend tens of thousands of dollars to design and build acoustically optimized spaces.  But you do not have to spend thousands to make your room sound good. For very little money you can make even the worst space sound good. So how?


First, we need to define two major aspects of your room treatment:

Acoustics and Sound Isolation

When we talk about the “acoustic room treatment” we are not talking about stopping construction noise from the street getting into your mic.  And we are not talking about your own voice annoying your neighbors.   These are examples of “soundproofing” or rather “sound isolation”  – stopping the transmission of sound from one point to another.  We can talk about this in a different article.

Room acoustics, or the way the sound generated inside the room behaves within the room itself, has very little to do with the ability of the sound to go through the barriers and spread out ( or into) your recording space. The approach is different, the materials are different as well.

People often get this confused, but materials used to “soundproof” your room will do nothing for helping your room acoustically and actually in some cases can make it even worse.


So what is Sound?

“Sound”  in most people experience is what we can hear.  In physics, “sound” is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a transmission medium such as air or water.

So basically sound is the energy of vibration, and that energy requires some sort of medium to spread around.  It spreads by agitating/vibrating adjacent molecules in the medium, so it can go through the air, water, steel etc. The denser the medium the faster it travels.  In the absence of a medium, such as in vacuum it ( sound energy) cannot spread so there is no sound in Space.

Since it is the energy of vibration, sound travels in waves. Called “soundwaves”.  Like if you wave your hand in a bathtub water you will create waves.  In this example your “vibrating” hand simulates a sound source and the waves in the water will be like “sound waves” spreading all around the tub.

Now you can wave your hand faster or more slowly and with more force, the resulting waves in the tub will also change the pattern.  That wave pattern is important in understanding of basic characteristics of sound:  Frequency, Wave length, Amplitude and Phase.

Try to vibrate your hand fast and easy – the resulting waves will be shallow, frequent and low in height. It will require very little effort on your part to make them.

Now try to wave your hand wider and more forcefully , this will be much harder to do and the waves will be deeper/higher and then will come not as often, and most probably will splash out of the bathtub because they are so high and strong.

You will also notice that the waves are bouncing back from the walls of the bathtub.  You can stop and watch what happens to the waves after you stopped generating more of them.

What you just did you created a model of how the sound waves work. A model that you can actually see.

Have that image in mind this might make it easier to understand how the sound works.


Sound waves and Frequency

Sound travels in waves.  Unlike your bathtub water waves, sound creates area of Dense (wave peak) and Rare (wave valley) pressure, because the sound spreads in all directions at the same time (omnidirectionally).  The frequency of the waves or how fast and how often the waves come, determine the pitch of the sound.  Frequency is measured in Hz (“Hertz”, after Heinrich Hertz, who had described this first). The higher the frequency, the higher the note. 

Human ear generally can hear between 20 to 20 000 Hz.  Sound above 20 000 inaudible to the human ear is called ultrasound.  Ultrasound is used by some animals for echolocation.

Sounds below 20 Hz called Infrasound. Infrasounds used for communication by some animals and also by people for monitoring earthquakes (seismic activity).

But for acoustic purposes we are mostly concerned with the audible range of frequencies.  And the related aspect here is “frequency response” .

 Frequency response refers to the way a microphone responds to different frequencies. It is a characteristic of all microphones that some frequencies are exaggerated and others are attenuated (reduced). For example, a frequency response which favours high frequencies means that the resulting audio output will sound more trebly than the original sound.

Ideally response should be the same for all frequencies or “flat response” .  This is virtually impossible to do, so the goal here is to “smooth things out”.


Amplitude of Sound

This is the Volume of sound, that measured in dB.  A decibel is defined as the smallest volume that can be perceived by human ear in isolation.  ( note “in isolation” means without reference to another sound. In reference to another sound trained ear can perceive sound volume changes as low as 1/10th of a decibel). 

A very quiet professional recording studio may have 30 to 40 dB of background noise, while Jet airplane engine can produce 140 dB of noise. This is not that the Jet engine noise is only 4-5 times louder than a professional recording studio, but dB level is measured on a logarithmic scale. In approximation, every 10 dB difference is about a 100 times change in sound energy level.



Wavelength is the length of a sound wave.  (did I have to explain that?)  It is related to the frequency of the sound waves. The higher the frequency – the shorter then waves. The lower the frequency the longer the waves.  Think of the bathtub example or the ocean.  On a nice calm day, you can see multiple small shallow waves coming onshore in brief succession.   Or you can see huge long waves crashing against the rocks during a storm.

The wavelength is important in combination with “phase” when dealing with room acoustics.



As the ocean waves have the Peaks and valleys, the sound waves also have the peak and trough. The term “phase” describes the relationship of two waves in time. If two identical waves that are at the different points of their cycle are combined, they may cause problems.

Phase is important in the acoustics and recording because the waves that are out of phase can cancel each other or vice versa reinforce each other resulting in tonal changes.

Phase problems occur when the sound bounces around the room.  Sound reflection is not a characteristic of sound per se, but it plays a major role in the room acoustics.  The reflective waves interfere with each other destructively, causing all sorts of problems.  Sound intensity near the hard surfaces because reflected wave adds to the original sound wave.

So Reflection control will be our next topic.



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