Equalizer

Equalizer, or EQ is sophisticated frequency control, which allow you to boost or minimize a range of frequencies, At its simplest, an equalizer divides audio signals into low, mid, and high frequencies. For example, you could increase the gain on the bass (the low frequencies) in your favorite dance music.

A common type of equalizer is the 1/3 octave equalizer, sometimes called a graphic equalizer. The graphic equalizer has 31 control points over the 10 octave to raise and lower the gain of the center frequency labeled above the control.

Limiter

Limiter are the same as compressor except that signals exceeding the threshold level are reduced at ratios of 10:1 or greater. Limiter can be set to prevent all signal from going above the given amplitude. Prevent the audio signal from being too intense, causing distortion or damage to the loudspeakers.

An example showing the use of a limiter:
The sound of a dropped microphone may be too intense, and cause damage to the audio system's loudspeaker.

Compressor

Compressor control the overall amplitude of a signal by reducing that part of the signal which exceeds an adjustable level (threshold) se by the user. When the signal exceeds the threshold level, the overall amplitude is reduced by a ratio, also usually adjustable by the user. For example, if the ratio of compression is set for 2:1, any part of the signal exceeding the threshold level is reduced by one-half. Compressor are used for reducing the overall dynamic range between the loudest and quietest signals. Compressor has ratio settings that are typically anything above 1:1 up to 10:1

Audio Signal Distortion

In any part of a system (amplifier, equalizer, cable, etc), there is an ideal, expected output signal waveform. Any false reproduction of audio is considered signal distortion.

The most common example of distortion occurs in analog equipment when the capabilities of the gear that receives of delivers the signal are exceeded. The amplitude of a signal must fall in a certain range to be accurately received by the device. The better quality the device, the more accurately it will handle the signal (less distortion).

The original signal is beyond the threshold, so the resulting signal is squared off.

If the amplitude of the sugnal is too low or to high for the device, it may be less inteleligible because of signal distrortion. The distorted sound is actually the odd harmonics of the signal being amplified and then added back into the signal.

Manufacturers generally specifify their product to be within a certain allowable tolerance of total harmonic distortion (THD). THD is generally given as a small percentage of the total signal, and measured at the maximum specifies output of the device.

Telephone conversations, not known for their audio quality, generally tolerate up to 10 percent distortion. In professional AV systems, a 1 pecent THD is noticeable to most.

It is up to the AV systems professional to assure that the installed system adheres to this tolerance by assuring the system is designed, set up and adjusted so that each item of equipment is getting and delifering the signal levels within the limits stated by the manufactures.

Noise Masking Systems

The purpose of noise masking systems is, simply, to mask noise. In the quiet, nonreverberant office spaces, conversations can be unintentionally overheard, invading privacy and mechanical or man-made noise can become disruptive to the work effort. When properly installed and balanced, the noise masking system makes these noises less noticeable. This can increase efficiency of the workforce as well as privacy.
Direct sound, so important for speech intelligibility in paging or reinforcement systems, is undersirable in masking systems. Loudspeakers, completely separate from paging loudspeakers, are throughtout the area. They are sometimes oriented horizontally to improve dispersion and avoid a spatial concentration of volume. When used properly, employees will not notice the installation at all, just that distruptive noise seem to be less noticable

High Pressure and Distributed systems

Feedback

Feedback is generated between a microphone and a loudspeaker when the same tone is caught in a loop an amplified again and again. This may happen when the volume of a certain sound is too loud; the audio system may be too loud or the source (the person talking) may be too far away from the microphone.


the avoid feedback poblems:
1) place microphone near the person, and physically as far from and behind the loudspeakers as possible.
2) Avoid placing microphones directly underneath ceiling mounted-speaker systems. Also, coach your presenters so that they cab avoid walkin underneath ceiling -mounted speakes
3)the presenter should stand at an appropriate distance from the microphoneor about 6 in. (15cm) away for a wires microphone. If the presenter is too far away, you may be empted to turn up the volume of the microphones output and that may cause feedback.
4) Beware of having too many open microphones at one time. Utilize the mute butons on a mixer to manage the microphones beter. You can also keep the gain (volume) lowered unused microphones.
5) Avoid placing too many microphone too close to each other.
6) Proper placement of a lavalier microphone on the presenter is critical to good microphone performance.


Feedback is best reduced through a combination of good loudspeaker placement and processing equipment. If the placement cannot be corrected, turn down the microphone or loudspeaker. Once the problem is corrected the result isnt instantaneous: it might take a second for the feedback o complete a cycle and die out.


Feedback also occurs uring audio and video conferencing. It manifests itself in the form of an echo or more feedback. The solution to this problem is often simple. Move the microphone away fom he loudspeaker or turn down the incoming or outgoing audi. There are many ways to resolve this problem, speak to a qualified professional.


best practices for controllong feedback include;
1) Keeping the microphone as close to the sound source as possible.
2) Keeping the loudspeakers in front of, and as far from the microphones as possible.
3) Selecting microphones with pickup patterns that complement the application.
4) Selecting loudspeakers with sound patterns that complement the application.


These practices will help increase your headroom - the maximum gain possible before feedback.That means how much power, which is translated to volume, can be achieved by the system before feedback occurs. Why does feedback occur with the power? Well, if you increase the volume too much, the sound waves from the loudspeaker have enough power toreach the microphone, causing the re-amplification of the same signal. If your loudspeakers output 70dB for a good listening level, abd feedback occurs in your