Audio & Acoustic Principles
Wired Microphones
Mixers & Audio Processors
Wireless Audio Products

Audio & Acoustic Principles

Can I make my microphone ignore room reverberation?
No. Microphones do not have "selective hearing", therefore if they are placed beyond the Critical Distance for that particular room, they will "hear" just as much, if not more, room reverberation than direct sound.
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My microphone is 5 feet from the closest talker. Is there anything I can do to decrease the amount of noise and reverberant sound picked up by the mic besides acoustical room treatment?
No. Short of room treatment, the only solution is to move the microphone closer to the talker. A Uni.-directional microphone might improve signal to reverberation ratio by 3 to 6 dB over an Omni-directional.
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Do additional open microphones decrease the gain before feedback of a sound system?
Yes. Every time you double the number of open microphones, the amount of gain available before the sound system will feedback decreases by 3 dB.
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What happens when a microphone is moved further away from a sound source?
Every time the distance between a microphone and a sound source is doubled, the microphone output for that sound source decreases by 6dB.
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Can I use equalization to reduce distortion in my sound system?
No. Equalization does not allow you to "fix" an already distorted signal.
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Will boosting high frequencies increase speech intelligibility?
Not necessarily. The majority of speech intelligibility for the human voice is centered in the 1 - 2 kHz range. Boosting frequencies above this range may increase sibilance, but is not crucial to intelligibility.
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Do I need to use a transformer when connecting a low impedance mic to a high impedance input?
Technically, a low impedance mic can be connected to a high impedance input directly without any significant signal loss, but it is usually a good idea to use a transformer due to the fact that most high impedance inputs require a higher signal level than is produced by a typical low impedance mic.
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Can I use a transformer to increase signal level?
Yes, but only to a maximum of 25dB, and there may be other losses involved.
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Is it necessary to match impedance when connecting two audio devices?
No. Actually, it is better to avoid matching impedance. In modern audio systems, an exact match (600 Ohm to 600 Ohm, for example) will result in a 6 dB loss of signal, whereas connecting a low impedance source (150 Ohm mic) to a higher impedance load (1000 Ohm mixer input) will result in almost no signal loss. This is referred to as bridging.
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What will happen if I connect a high impedance mic to a low impedance input?
There will be excessive signal loss due to the impedance mismatch, essentially making the signal unusable.
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Can I get acceptable sound quality from microphones placed on a ceiling?
Probably not. Placing a microphone on a ceiling puts it farther away from the desired sound source (the talkers) and closer to undesired sound sources (loudspeakers, air handling, etc.).
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Are microphones with higher sensitivity ratings better?
Not necessarily. The sensitivity of a microphone is not related to sound quality, nor is a highly sensitive microphone desirable for all applications (kick drum, for instance).
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Do all microphone manufacturers rate their sensitivity levels in the same way?
No. Microphone sensitivity must be measured in reference to a specific sound pressure level. Some manufacturers use 94 dB SPL (1 Pascal) and some use 74 dB SPL (1 microbar).
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Is it possible to measure how many feet away my microphone can "reach"?
No. There is no such thing as microphone "reach". A microphone only responds to sounds that enter its pick-up area, but it cannot "reach out" to pick up sounds. Microphone polar pattern and ambient sound levels contribute to how far away a microphone can be placed from a desired sound source and deliver acceptable results.
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Does a directional microphone "enhance" sounds that originate in front of the microphone?
No. Directional mics ignore, or are less sensitive to, sounds that originate from the rear or the side, but they do not "enhance" sound from the front.
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Mixers & Audio Processors

Are phantom power and bias voltage the same thing?
No. Phantom power is typically 11-52 Vdc that is supplied on the audio conductors of a balanced mic line. Bias voltage is usually lower (1.5-9 Vdc) and requires its own conductor. The two are not interchangeable.
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Is there a difference between a VU and a PPM audio meter?
Yes. A VU meter displays the average volume level of an audio signal, while a PPM meter shows peak volume level. These differences must be taken into account when aligning a VU meter with a PPM meter.
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Can I rely solely on my meter to accurately set levels?
No. While meters are a useful aid for setting levels, critical listening is the best way to ensure a clean, strong audio signal.
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Are automatic microphone mixers necessary when there are 8 or more open microphones?
Yes. An automatic mixer will reduce amplification of background noise, increase gain before feedback, and reduce comb filtering.
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Is an automatic mixer faster than a human operator?
Yes. A Shure automatic mixer can activate a microphone within 4 milliseconds.
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Can I use two wireless microphones with one receiver?
Absolutely not! A wireless receiver can only demodulate the signal from one active transmitter at a time.

What is the pin-out for Shure bodypack transmitters?
Any Shure bodypacks that use a Switchcraft TA-4F connector are wired as follows:
Pin 1: Shield
Pin 2: Bias (+5Vdc)
Pin 3: Audio
Pin 4: 20 k Ohm resistor to ground (for use with some condenser microphones)

Are traveling frequencies a good way to avoid interference anywhere in the country?
Not necessarily. While traveling frequencies allow you to avoid broadcast television anywhere in the U.S., there are many other forms of RF interference present in this frequency band (169-172 MHz).
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Is there a limit to the number of traveling frequencies I can use at one time?
Yes. A maximum of three traveling frequencies can be used in any given location at one time.
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Is there any way to locate possible sources of RF interference before purchasing a wireless system?
Yes. The best way to find interference beforehand is to use an RF scanner. This simple device allows you to scan frequencies for potential interference. Another helpful tool is a map of all licensed transmitters in a given area, such as those produced by RadioMap.
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Will I have to stop using my wireless system during the DTV transition?
No! The FCC has agreed to allow all low-power auxiliary stations (primarily wireless microphone systems) to continue operation. Wireless microphone systems are not being "kicked-out" of any particular frequency range.
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