Recording sound

[BRIANP]

when recording, what will give you better sound,a larger umbrella or a smaller one if the microphone is placed in the center of it, what would happen if I used a card board box? do the densities of the materials used deaden or amplify the sound? What shape is best for a concert hall and why?<br>

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thanks for the info<br>

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brian powell, 8th grade

 

[Lovecow]

The advantages and disadvantages of using of an &quot;umbrella&quot; around a microphone is dependent on your application. I assume you are talking about a parabolic reflector, like the ones seen on the sidelines of many football games. These are used to focus the sound coming from a specific area on the field towards to microphone. This type of system is used whenever one wishes to focus on a sound field, much like a telescope is used to focus on a visual field.<br>
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The reflector's size will govern the frequency range of sounds that are reflected towards the microphone. Frequencies with a wavelength near to or larger than the reflector will not focus very well. Frequencies small compared to the size of the reflector will focus quite nicely.<br>
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The material of the reflector needs to be acoustically reflective for the freqeuncy range of interest. Plexiglass or some form of hard, stiff plastic is usually employed. Cardboard may work, but may require reinforcement so that (a) it retains its shape and (b) certain frequencies aren't absorbed by the cardboard's resonances.<br>
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Some materials will deaden the sound. The preferred materials will not. There are no materials that can &quot;amplify&quot; in this application. All materials will display some small amount of absorption no matter how hard and stiff they are.<br>
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Finally, there are many shapes used in concert hall design. Some good, some acceptable and some horrible choices are out there. Generally, there not a single &quot;best shape&quot;. Many books have been written on good concert hall design. An expert acoustician will be able to work with architects and engineers to maximize the acoustical benefits of any concert hall design.