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”?
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:
- Room within a room (RWAR)
- Noise cancellation
- Residential soundproofing
- Commercial soundproofing
- Automotive soundproofing
- Exterior soundproofing
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.
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.
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.
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”.
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:
- Cell size
- Material thickness
- Material density
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 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!