Sound Acoustics

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  • Topic: Sound, Acoustics, Noise pollution
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  • Published : March 25, 2013
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Indoor & Outdoor Acoustic Sounds

Indoor Acoustics
The Principles of Sound and Acoustics
Sound is the apparent vibration of air resulting from the vibration of a sound source (e.g. guitar sound board, hair dryer, etc). We can describe such regular vibration in terms of the sum of simpler vibrations (harmonics). In other words any periodic oscillation and hence resulting waveform can be described in terms of the sum of its harmonics. Each harmonic being a simple sine wave (often called a pure tone) with it’s own respective frequency and amplitude.

Studio-based Acoustics
When you're trying to set up a studio on a limited budget, it's all too easy to concentrate on buying equipment rather than spending your hard-earned cash on things that don't make a sound. A little money spent treating the room in which your studio is based, however, can often be a better investment. A lot of people find out too late that the acoustics of their chosen room cause problems, either by colouring their recordings, distorting their monitoring perspective or leaking sound.

Live Room
The typical recording studio consists of a room called the "studio" or "live room", where instrumentalists and vocalists perform; and the "control room", which houses the professional audio equipment for either analogue or digital recording, routing and manipulating the sound. Often, there will be smaller rooms called "isolation booths" present to accommodate loud instruments such as drums or electric guitar, to keep these sounds from being audible to the microphones that are capturing the sounds from other instruments, or to provide "drier" rooms for recording vocals or quieter acoustic instruments.

Dead Room
A lot of studios pride themselves in having a ‘dead’ room. What does this that mean? * It’s free and clear of ambient noise
* It has enough treatments in it to soak up any sound made in the room (so as not to hear an echo). When recording at home, sometimes it’s hard to get a dead room. Heating/AC vents, windows, neighbors, etc. all contribute to those ambient noises that you’re trying to keep out of your recording. You can also be the culprit with loose clothing, watches, a squeaky chair, computer fan, and even things like moving papers around.

Surface types and properties;
When a sound wave meets an obstacle, some of the sound is reflected back from the front surface and some of the sound passes into the obstacle material, where it is absorbed or transmitted through the material. Reflection and absorption are dependent on the wavelength of the sound. The percentage of the sound transmitted through an obstacle depends on how much sound is reflected and how much is absorbed. We are assuming that the obstacle is relatively large, such that no sound passes around the edges. When a sound wave in air reaches the surface of another material, some of the sound is reflected off the surface, while the rest of it goes into the material. For example, when sound hits a wall, some is reflected and some passes into the wall. If the surface that the sound wave hits is relatively smooth, more sound will be reflected than if the surface is rough. For example, more sound will be reflected from a smooth wall made of mud than a pile of dirt. The reason is that the rough or porous surface allows for many internal reflections, resulting in more absorption and less reflection. Some materials absorb sound more than others. Drapes and ceiling tiles are used to absorb unwanted sound and eliminate echoes. Music recording studios use sound absorbing materials on their walls to eliminate any undesired or outside sounds, when recording a song.

Reverberation;
Reverberation is the persistence of sound in a particular space after the original sound is removed. Originally, the studio recordings were performed through the microphone quite remote from the sound source. This microphone, like the human ear, received the sound waves reflected from the walls of...
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