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Entries found for search: frequency

audio frequency : See AF.

center frequency : The frequency that is boosted or attenuated most by the operation of any parametric equalizer or other similar processing device or circuit. See Q.

corner frequency : See rolloff frequency.

critical frequency : See rolloff frequency.

crossover frequency : The frequency above and below which an audio signal is divided into two bands, each of which is directed to a separate destination. Precisely, the frequency at which each of the two bands is attenuated 3dB by the crossover network.

cutoff frequency : See rolloff frequency.

erase frequency : See erase head.

extinction frequency : In magnetic tape recording, the high frequency beyond which significant cancellation occurs because its wavelength on tape, at the specified tape speed, approaches the width of the head gap.

reference frequency : See line-up tone.

frequency response errors : Any deviation from a linear output response in an audio device.

frequency : The number of waves (or cycles) arriving at or passing a point in one second, expressed in Hertz. See pitch, Appendix D.

frequency distortion : Frequency distortion results when the amplitude of the output of a system or a device varies as the frequency of the input varies, while the amplitude of the input is held constant.

frequency doubling : See doubling.

frequency masking : An audio artifact which occurs when several sounds are mixed, all which occur in the same frequency range. This happens because human ears tend to blend simultaneous sounds into a single, composite sound. When several instruments or other sounds emphasize similar frequencies, those frequencies accumulate and can either become too dominant or can cause one sound to mask another. Also called band masking or auditory masking.

frequency modulation (FM) : (1) A change in the frequency (pitch) of a signal. At low modulation rates, FM is perceived as vibrato or some type of trill. When the modulation wave is in the audio range, FM is perceived as a change in timbre. FM synthesizers, commonly found on soundcards, create sounds using audio-range frequency modulation. See FM synthesis. (2) Frequency modulation is the instantaneous changing of the frequency of a carrier in response to a modulation signal, usually an audio waveform. As the signal voltage varies up and down as it follows the waveform, the frequency of the carrier varies up and down from its nominal unmodulated value. The FM receiver is tuned to the carrier frequency, and the received signal, after suitable conditioning, is applied to a special circuit called an FM detector, also called a demodulator or discriminator, which recovers the audio signal. See amplitude modulation.

frequency modulation distortio : Examples of frequency modulation distortion are flutter and wow, and Doppler distortion caused by the motion of rotary (Leslie) loudspeaker cones.

frequency ratio : The ratio of the higher pitch in an interval to the lower pitch. See consonant, harmonic.

frequency response : The amplitude response of a system or device as a function of the input frequency characteristic. It is a complex function which describes the way in which the gain and phase of a system or device vary with the frequency of the stimulus. Frequency response is a characteristic of a system or device, not a characteristic of a signal. See linear.

frequency response curve : A graph of the frequency response of a device, i.e., the graph of its output amplitude response vs. the input frequency. See linear. For example, tThe frequency response curve for a microphone is a graph of the micís output level in dBindB at various frequencies. The output level at 1kHz is placed on the 0dB line and the levels at other frequencies are placed above or below that reference level. The shape of the response curve suggests how the mic sounds; a wide, flat response tends to sound accurate and natural. A rising high end or a presence peak around 5-10kHz sounds more crisp and articulate. Note that the response curve is measured at a specified distance from the mic, usually 2-3 feet; the curve reflects the performance of the microphone only for that particular distance.

frequency shifter : A device that linearly shifts all the frequencies of a complex input signal. Also called a spectrum shifter. All frequency components are shifted linearly, i.e., by the same number of Hertz, in contrast to a pitch-shift caused by changing the speed of a tape-reco. In such a pitch-shift, all the frequency components are shifted by a constant percentage, and therefore, high frequencies are shifted proportionally more than lower ones. A pitch-shift-by-speed change thus preserves all the musical intervals between components. A true frequency shifter, in contrast, destroys the harmonic relationships between the components. The sound of a consonant musical tone becomes disconsonant or clangorous or harsh, depending on the amount of shift. Frequency shifters are used in electronic music synthesizers for special effects.

high-frequency compression : See HX/HX pro.

low-frequency oscillator : See LFO.

rolloff frequency : The frequency above or below which a filter begins to filter out the harmonics of the waveform. As the rolloff frequency is raised or lowered, more of the harmonics of the sound will be filtered out. Specifically, the frequency at which the response of an equalizer or other audio device is reduced by 3dB,. This is also sometimes called the half-power point and can refer to both lowpass and highpass response curves. The rolloff frequencies of an amplifier are the frequencies where the output voltage drops to 0.707 of the middle range output. A decrease of the voltage by a factor of 0.707 is equivalent to -3dB, so these critical frequencies are often referred to as the 3dB down points. Also called cutoff frequency, critical frequency, or the half-power point. Moving the rolloff frequency in real-time will produce a wow effect, which can be accentuated by increasing the filter resonance level.

resonant frequency : See resonance, loudspeakers.

radio frequency (RF) : An alternating AC current or voltage having a frequency above about 100kHz, so-called because these frequencies are radiated as electro-magnetic waves by radio and television, and as high as 30 GHz (30,000 MHz). The constant frequency of the carrier wave (the frequency which you tune into) falls within this range. This is then modulated by the audio (or other) signal, according to some process such as AM or FM.

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