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What is “Soundproof”? – Start learning!

Looking to improve your relationship with your neighbours by not annoying them too much with your world class guitar playing? Then you have come to the right place. Here, we will answer the age old question that any home recording enthusiast would be asking – What is “soundproof”?

If you are thinking of ways to have a quieter, more isolated practice sessions at night, or to have a cleaner and better sounding recording, then you need to know the different aspects of soundproofing. In this article, we will discuss the various concepts surrounding the subject of soundproofing, and also its application in our daily lives.

What is “Soundproofing”?

Anechoic Chamber

Photo by Tlotoxl / CC BY-SA 3.0

The process of making a room or a venue “soundproof” is called soundproofing. This process of soundproofing includes using any methods possible, to reduce the sound pressure in relation to a specified sound source and receptor.

Some of the various approaches to reducing sound includes, utilizing noise barriers to either reflect or absorb the energy coming from sound waves, using active “anti-noise” sound generators, or increasing the distance between sound source and receiver by using sound baffles (a type of damping structure).

When you are considering various acoustic treatments, do take note of two very important factors – improving the sound within a room (could be your bedroom), and preventing sound from leaking into or from adjacent rooms and outdoors. Methods such as acoustic quieting, noise mitigation, and noise control are often used to reduce unwanted noise.

Soundproofing also involves the suppression of unwanted indirect sound waves (reflections) that causes echoes and resonances, which will inevitably lead to “reverberation”. Another application of soundproofing is in the reduction of transmission of direct sound waves (unwanted) from a source to an involuntary listener. This is accomplished through using distance and intervening objects in the sound path.

Let us look at the different methods and aspects of soundproofing:

  • Distance
  • Damping
  • Absorption
  • Reflection
  • Diffusion
  • Room within a room (RWAR)
  • Noise cancellation
  • Residential soundproofing
  • Commercial soundproofing
  • Automotive soundproofing
  • Exterior soundproofing

DistanceSound Distance

Based on the understanding that the energy density of sound waves will decrease as they spread out, we are now able to reduce the intensity of the sound level at the receiver, by increasing the distance between the receiver and the sound source. Just so you know, the attenuation of the intensity of sound waves, occurs according to the inverse square of the distance from the sound source.

Damping

This is the process of reducing resonance in a room, by absorption or redirection (otherwise known as reflection and diffusion respectively). Absorption is responsible for reducing the overall sound level, while redirection nullifies the harmful effects of unwanted sounds and can even make it beneficial by reducing coherence.

Acoustic Panel

Photo by User:Daniel Christensen / CC BY 3.0

Damping will also reduce acoustic resonance in the air, or mechanical resonance (which happens due to the structure of the room itself or objects in it). When soundproofing is integrated into the construction of a vehicle, a panel dampening material is usually fitted, which has the function of reducing vibrations from the vehicle’s body panels. These vibrations are caused by high energy sound sources that are triggered when the vehicle is in use.

Absorption

Absorbing sound involves converting part of the sound energy into a minuscule amount of heat, which resides in the intervening object (the absorbing material), rather than allowing the sound to be transmitted or reflected. There are a few ways in which various materials absorb sound. When looking for a sound absorbing material, bear in mind the frequency distribution of noise (to be absorbed) and the acoustic absorption properties required.

The two types of absorbers are “Porous absorbers” and “Resonant absorbers”.

Porous absorbers

These are your typical open cell rubber foams or melamine sponges, they absorb noise by friction within the cell structure. Porous open cell foams would be a great choice as they are highly effective in absorbing noise across a wide range of medium-high frequencies. However, it is less effective when dealing with low frequencies.

The absorption properties of a porous open cell foam is determined by the following factors:

Acoustic Foam

Photo by Trevor Cox / CC BY-SA 2.0

  • Cell size
  • Tortuosity
  • Porosity
  • Material thickness
  • Material density

Resonant absorbers

Resonant absorbers such as resonant panels, Helmholtz resonators and others work by damping a sound wave as they reflect it. Different than porous absorbers, resonant absorbers would be ideal in dealing with low-medium range frequencies and resonant absorbers also absorbs a more narrow range of frequencies.

Reflection

A very simple concept, but highly effective nonetheless. Especially used in outdoor environments such as a highway engineering, “embankments” or “panelling” will be used, in order to reflect sound upwards into the sky.

DiffusionSound reflection diagram

If you are experiencing a problematic echo due to a specular reflection (mirror-like reflection of sound) from a hard flat surface, then you would want to have an “acoustic diffuser” to be applied onto the surface. This will help to scatter sound in all directions.

Room within a room

Also referred to as (RWAR), it is known as an effective method of sound isolation and it also prevents sound from transmitting to the outside world where it may be an inconvenience.

Sound waves (vibrations) can only be transferred from the sound source (inside the room) to the outside through mechanical means. These vibrations will pass directly through various solid elements such as bricks and woodwork. When the vibrations come into contact with elements such as a wall, ceiling, floor or window, these surfaces act as a sounding board, which causes the vibrations to be amplified and heard in the second space.

Studio Construction

Photo by superscalevp / CC BY 3.0

As compared to an airborne transmission, a mechanical one is much faster, more effective and allows the sound waves to be readily amplified. Keep in mind that this comparison is made with the sound sources having the same initial strength.

You could try using acoustic foams and other absorbent material, however, it is not effective against this type of transmitted vibration. It is advisable to try and break the connection between the room (where the sound source comes from) and the outside world. This is known as acoustic decoupling.

The ideal decoupling method will involve eliminating vibration transfer in both solid (walls,ceiling etc.) and in air, thus the air-flow into the room must be controlled. However, there are safety measures that needs to be taken, which includes ensuring proper ventilation inside the decoupled space, and gas heaters cannot be used.

Noise cancellation

Noise cancelling

Photo by Marekich / CC BY-SA 3.0

This method requires “noise cancellation generators” for active noise control. But this is a rather modern innovation and not a very popular one as well. It works by using a microphone to pick up sound (in the room) that is then analysed by a software (in a computer), and afterwards, sound waves with inverted phase (180° phase inversion at all frequencies) will be played through a speaker, thus acting as an interference and will cancel much of the noise.

Residential soundproofing

This concept simply aims to either decrease, or eliminate noises coming from the outside. In most cases, residential soundproofing puts focus on any windows in the room. You can use curtains (made of heavy material) to damp sound or air chambers called “honeycombs”. There are various layers of honeycomb designs that yield varying results in sound damping.

Acoustic Curtain

Photo by Greg O’Beirne / CC BY 2.5

The downside of using curtains however, is the absence of a seal at the edge of the curtain. To rectify this, use sealing tools such as hook and loop fastener, adhesive, magnets, or other materials.

You can also achieve much better sound damping by modifying your single-pane windows. By installing a second interior window, further noise reduction can be attained . The most common design would see that the exterior window remaining in place, with a slider or hung window being built within the same wall openings.

Commercial soundproofing

Businesses also sometimes see the benefit of incorporating soundproofing technology into their facilities. Bars, schools, and medical facilities alike, make use architectural acoustics for noise reduction. You will even see office buildings utilizing soundproofing concepts in order to try and make cubicle spaces more conducive for workers using the phone.

Automotive soundproofing

Automotive Soundproofing

Photo by corvettewebcentral / CC BY 3.0

This concept of soundproofing aims to reduce or entirely eliminate the impact of exterior noise, primarily caused by the engine, exhaust and tires. Due to the nature of the automotive industry, there is a limit to the thickness of materials that can be used, however the use of dampers, barriers, and absorbers are very common.

If you are a driver yourself, you would know that complex noises are created within vehicles which is determined by the driving environment and speed of the vehicle. It is believed that noise reductions (up to 8 dB) is possible by installing a combination of all types of materials.

Exterior soundproofing

Starting in the 1970s, it is not uncommon to see most industrialized countries building noise barriers along major highways, in order to protect nearby residents from undesirable traffic noise. Over the years, new techniques have been engineered to better predict an effective design for the noise barrier, in order to suit a particular real world event.

Noise Barrier

Photo by Michiel1972 from nl / CC BY-SA 3.0

Noise barriers are made of various materials including wood, masonry, earth or even a combination of them. The earliest known noise barrier was in Arlington, Virginia adjacent to Interstate 66, and the idea was born from concerns expressed by the Arlington Coalition on Transportation. Another one of the earlier noise barrier constructions (scientifically engineered and published) was said to be in Los Altos, California in 1970.

Had enough of soundproofing yet? Want more? Well, I am afraid that is all the information I can provide for now. Hope you people have got something useful out of it, and would want to try incorporating some of these concepts into your own home studio.

Thanks for reading, and do leave comments below. Till next time, cheers!

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Farhan

When I'm not rocking out to great music, I'd prefer to be sleeping on a field on a windy day =)

10 Comments

  1. Very informative post on sound proof and all the possible method used to soundproof a room. What method would you recommend I use when doing voice recording on my studio software laptop using a cushion protected microphone?

    I am quite eager to learn how to self soundproof my bedroom and how to go about gathering all the required materials including fibre glass. Thanks for this post Farhan.

    • Hi Tebatso!

      I am happy to know that you find this article to be informative!

      When you say “cushion protected”, I will just assume you meant “microphone windscreen” here. Microphone windscreens are very common and in my opinion, do not require any “special” soundproofing method (other than the ones I have pointed out).

      However, do remember to clean your windscreen regularly, as they tend to collect dirt and moisture in their open cells, and this will cause a “high frequency loss” in your vocal recordings. It is also unhygienic and unhealthy, especially if you are sharing it with other people.

      I would recommend that you use “vocal booths” for your vocal recordings. Do take a look at this article – http://myaudioeducation.com/home-studio-recording-

      That article will explain more on vocal booths and also provide tips for better home recordings!

      Cheers =)

  2. I know from when I have experimented with music recording in the past that having a properly soundproofed studio makes all the difference in quality. It is not just about keeping sound from escaping, as your article explains so well, it is also about stopping sound reverberating around and causing unwanted distortion. You are very good at explaining these complicated technicalities so well, Farhan, keep up the good work!

    • Hello Molly!

      Thank you for your kind comments. Yes, I do try my very best to explain these concepts in a way that is accessible to beginners or people who are just new to this.

      Thanks again for the encouragement, and do come back for more!

      Cheers =)

  3. Hey, this was a great article.

    The problem that a lot of home studio owners have is setting up their microphones in a way that doesn’t pick up a lot of external noise. Also, the ability to monitor the sound when mixing is another issue that faces home studios.

    This article was excellent because it teaches people how to get around these issues.

    Great stuff.

    • Hey there! Thanks for dropping by!

      I am glad you have found this article useful. Do check back for more!

      Cheers =)

  4. Hey FarhanSidik,

    I just read your article on soundproofing, and wanted to know how much would it cost for a soundproof. Is it really pricey? and if so whats the cheapest high quality soundproofing I can get, if that makes any sense lol? I just feel like the walls are too thin in the house im living in right now and that would be of great help to me.

    • Hello kelechukwu!

      Thanks for dropping by. You need to understand nobody actually totally soundproofs their rooms, as it is way too expensive. Professional recording studios spend millions on just soundproofing and optimizing the acoustics.

      Look into acoustic curtains, they cost anywhere from $80-$100 (depending on dimensions and material). You can also look for acoustic foams that will cost you anywhere from $10-$15 per piece. Note that these are affordable options for improving acoustics in your room, and also to reduce noise coming from outside or from inside your room.

      If you are really serious in isolating sound in your room, then you need to be ready to move into re-construction methods like “room within a room” which will cost you thousands of dollars to say the least.

      Hope that helps =)

  5. Hey! this is a great website, very informative, i am still new to web design but i found this site to be nicely put together. I think its a good idea to really differentiate between sound proofing and acoustic treatment, they are two completely different things. True soundproofing means air tight and AC units too, very difficult in a residential place although we can all dream! Great work !

    • Hi Rob!

      Thanks a lot for your thoughtful comments. I am always looking for ways to improve the quality of the content on this site. I am glad that you have found this site beneficial!

      Do come back for more!

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