1. B standard stereo
One of the stereo sound pickup methods uses two microphones with exactly the same sensitivity and directivity (commonly used cardioid directivity), and the distance between each other is about 1.5 to 2 meters (also can be reduced to 0.5 meters, depending on the width of the sound source arrangement) , Placed in front of the sound source to pick up the sound, and then output with the left and right channel signals respectively. The advantage is that it is simple and easy to use, the sound picked up is full of naturalness, and the pickup method is mainly based on time difference. The existence of time difference can reflect the early reflections of more concert halls. It has a good sense of scene and is suitable for recording classical symphony. The disadvantage is that if the two microphones are far apart, there will be voids and depressions in the middle when listening. If a sound source moves laterally, it will feel that the sound image passes through the middle faster and has a sense of jumping. In severe cases, it will make the sound The images are concentrated around the left and right speakers. If the left and right channel signals are mixed and played, sound interference will occur, so that the left and right channel signals of some frequencies are also enhanced and the reflections canceled. The frequency response of the output signal is the characteristic shape of the comb filter, resulting in The sound is unpleasant.
2.AC-3 decoder
It can decipher the surround sound decoders of AC-3 encoding, including pure AC-3 decoding, AC-3 decoding and Dolby Pro Logic Surround, and AC-3 decoding compatible with THX and Dolby Pro Logic Surround. The latter two are equipped with AV interfaces, which can be equipped with a variety of audio/video signals. The input ports are AC-3rf radio frequency data stream, digital optical cable and coaxial signal, and the output is only 5.1 channel front left and right, center, and rear. The 6 terminals of surround left and right and subwoofer output have no AV interface and no volume. They must be used in conjunction with other AV power amplifiers.
3.AV power amplifier
That is, the amplifier used in the audio-visual system is used in the audio-visual system of the home theater, and the power amplifier is complete. AV power amplifiers generally have 4~7 channel power outputs such as front, center, surround, etc., and some have Dolby Pro Logic surround decoder or AC-3 decoder, DSP digital sound field processing, and FM/AM digital tuning radio It also has a variety of audio input and output interfaces. Some power amplifiers also have a SVIDEO (high-definition) video four-pin interface. Various functions can be controlled with a remote control, which is very convenient to use.
4. Background music
Continuously broadcast music in public places, based on the loudness standard that does not affect people's dialogue, can adjust people's mental state and create a comfortable and warm environment. Background music is usually not a stereo system, and speakers are mostly used for distributed playback, so the sound is evenly distributed, and the adverse sound environment has little effect on listening.
5. Octave
Two frequencies are compared to the frequency range between sounds of 2, and one octave is an octave pitch relationship, that is, for every doubling of the frequency, the pitch increases by one octave. The frequencies of the graphic equalizer Between the points is the octave relationship.
6. Double speed recording
When recording with a dual-card recorder, the function is set to save recording time. The tape speed of double-speed recording is twice that of normal recording, and the time spent is doubled. When monitoring the recording effect, the sound is played quickly and the pitch is increased. An octave.
7. bit
The bit in a binary number, the unit of measurement of the amount of information, is the smallest unit of the amount of information. In digital audio, electrical pulses are used to express audio signals. "1" represents pulses, and "0" represents pulse intervals. If the information of each point on the waveform is represented by a four-bit code, it is called 4 bits. The higher the number of bits, the more accurate the expression of analog signals and the stronger the ability to restore audio signals.
8. Marshalling output
One of the output forms of the mixer is to continue grouping and distributing the left and right channel signals after adjusting the sound and image of the mixer. Therefore, it is a stereo output mode. In general, the singular group is the left channel and the even number is grouped. For the right channel. Groups can be output individually, or they can be sent to the left and right main channels and then output from the left and right channels. The marshalling output is mostly used to send signals to the return speaker system, and it can also be used flexibly as needed.
9. Pitch shifter
A device that changes the pitch of accompaniment music. Due to the difference in the range of each person's vocal range, the accompaniment music required to sing is also different in pitch. Through the pitch shifter, the singer can sing in the appropriate range. The sound that has been raised by the pitch translator is pleasant, and the volume seems to be louder. This is because the human ear is more sensitive to the high pitch after the frequency is raised; after the pitch is lowered, the bass appears fuller, and the volume will be slightly lower. The pitch shifter uses electronic circuits to raise and lower the tone frequency of the music. Its working process includes sampling (measurement of frequency), separation (differentiation of fundamental and overtone), frequency conversion (change of frequency of fundamental and overtone), synthesis (Tone in synthetic music), correction (output according to calculation data) and display, etc., the falling key symbol is b, the rising key symbol is #, the music processed by the pitch shifter to raise or lower the key, and the tone recorded on the original carrier There is almost no difference.
10. Variable speed processing
Also known as audio time compression and expansion processing, it is a processing that changes the speed of tape playback without changing the tone of the sound. It is mostly used in professional situations. It is possible to appropriately extend or shorten the playing time of various programs that have been recorded without changing the timbre and pitch of the original sound, which provides an important means for real-time synchronized playback of programs. The method of changing the number of motor revolutions is used to adjust the playback speed and change the playback time. However, because the change in the speed of the tape will inevitably make the sound pitch higher or lower, the variable speed processing system is equipped with a signal frequency conversion circuit, which will change due to the speed change. The change in the tone of the sound caused by it is restored.
11. Transformer
An electrical appliance that transforms AC voltage, current, and impedance. It is generally used for AC voltage conversion or inter-stage coupling of audio amplifiers. During the audio connection of the system, the noise crosstalk, equipment mutual influence and power supply line interference, etc.
12. Wavelength
The distance traveled by a sound wave vibration once, the speed of the sound wave is divided by the frequency of the sound wave to calculate the wavelength of the sound wave at that frequency, and the effect of the wavelength of the sound wave. For example, only when the size of the obstacle is greater than one wavelength of the sound wave, the sound wave will be reflected normally, otherwise the diffraction, scattering and other phenomena will be aggravated, the sound shadow area will become smaller, and the acoustic characteristics will be different; another example is the sound field with a wavelength greater than 2 times. It is far fieldless, and the sound field less than twice the wavelength is called the near field. The sound field distribution and sound propagation law of the far field and the near field are very different; in addition, in a smaller room (compared to the wavelength), the bass It cannot be reproduced well. This is because the bass has a longer wavelength. Therefore, in ordinary households, if the volume of the listening room is not large enough, the bass effect is difficult to achieve the ideal state.
13. Parametric equalizer
Also known as a parametric equalizer, an equalizer that can finely adjust various parameters of the equalization adjustment is usually attached to the mixer, but there is also an independent parametric equalizer. Adjustable parameters include frequency band (such as low, mid-low, mid-high and high-frequency, etc.), frequency point (sweep type, can be arbitrarily selected), gain (boost attenuation) and quality factor Q (band width, with any adjustable type) And high-Q and low-Q options), etc., are generally used to subjectively adjust the sound, and for the needs of artistic creation, special processing of the sound signal. For example, the parametric equalizer can beautify (including ugly) and modify the sound, make the sound (or music) style more distinctive and colorful, and achieve the required artistic effect.
14, reverb
After the sound source stops sounding, due to inertia and reflections, the sound does not stop immediately, but slowly decays. In the sound system, the reverberation effect of the sound can be used to change the reverberation process of the sound and make the sound more rounded and fuller.
15, bad beat
The periodic change formed by the interaction of two sounds of different frequencies, the amplitude increases and decreases periodically according to the difference between the two frequencies, and the amplitude modulation of the sound volume and ups and downs appear. The same phenomenon exists in electrical signals.
16. Insert the connection
A connection method in which a peripheral device is directly connected to a device (mainly a mixer). The mixing console generally has an insert (INS) interface. You can use the insert connection method to insert a peripheral device into a certain input channel, group channel and main (left and right channel) channel, and process the sound signal of the inserted channel separately. The plug-in connection can be realized with the junior core, the method is to output the signal from the head end of the junior core, connect to the input end of the device to be inserted, and then send the signal from the output end of the device to the ring end of the junior core.
17, flutter echo
The sound vibration phenomenon caused by multiple reflections of sound between parallel walls is a serious sound building defect, which can cause unstable sound volume and poor sound quality. The most effective method of elimination is to avoid parallel walls, use strong sound-absorbing materials, and treat the surface of the wall into an uneven diffuse reflection structure.
18. Vibrato
Music embellishments obtained by using periodic changes in pitch, volume and timbre. The reasonable use of vibrato can make music more beautiful and appealing, and enhance the appeal of art. In a professional audio system, effects can be used to create and strengthen the vibrato effect.
19.Ultrashort wave
Also known as very high frequency (VHF) waves, meter waves (wavelength range of 1 meter to 10 meters), radio waves with frequencies from 30 MHz, transmission and insertion frequency bandwidth, short-distance propagation depends on electromagnetic radiation characteristics, used for television broadcasting and The wireless microphone transmits audio signals, and a sharp directional antenna is used to compensate for the attenuation of the transmission process. In the field of professional audio, the frequency stability of V-segment wireless microphones is slightly worse and the price is relatively low, but it is prone to frequency drift. Through various technical measures, the frequency stability can reach the level that meets the needs.
20, long wave
Radio waves with frequencies ranging from 3000 kilohertz to 30 kilohertz are mainly propagated in the form of ionospheric waves around the earth’s surface, with a range of up to thousands to tens of thousands of kilometers. In addition, at short distances (200 to 300 kilometers) Within) it can also be propagated by ground waves. The electric field intensity of this band increases at night than during the day. The shorter the wavelength, the greater the increase; the influence of the electric field intensity with the season is small; the propagation conditions are less affected by the ionospheric disturbance, and the stability is good. There will be no sudden changes in reception intensity and sudden interruption of communication.
21. Reserve power
The part of the power that exceeds the minimum output power of the power amplifier required by the speaker, or the power that reaches the required maximum sound pressure level. The greater the power reserve of the audio system (generally referred to as power amplifiers and speakers), the thicker and fuller the sound, the more powerful, and the greater the dynamic; on the contrary, when reproducing powerful and abrupt sound effects, it will sound hoarse and dull. In general, the power of the power amplifier should exceed 1.5 times the power of the speaker, but sometimes it can reach 3 times the power of the speaker.
22. Sound transmission medium
Refers to the medium that can transmit sound. Sound must be transmitted through the medium, such as gas, liquid, and solid. The properties of the medium, including its state, temperature, pressure, etc., are closely related to the speed and mode of sound wave propagation. For example, the sound propagation in gas is dominated by radiation characteristics, while the propagation in solids is dominated by conduction characteristics, and the above two characteristics exist when propagating in liquids.
23. Sound transmission gain
When the sound reinforcement system uses a microphone, the amplification of the sound picked up by the microphone is an important indicator for investigating the degree of sound reinforcement feedback. The higher the sound transmission gain, the smaller (less) the acoustic feedback whistling and the greater the amplification of the microphone sound. Large, the calculation method is to turn on the microphone volume to the maximum (no acoustic feedback phenomenon), put a sound source in front of the microphone, measure the sound pressure level in the sound field and before the microphone, and subtract the sound in front of the microphone by the sound pressure level in the sound field The pressure level is the sound transmission gain of the sound reinforcement system. Transmission frequency characteristics The frequency response characteristics of the sound reinforcement system are the common frequency response characteristics of the room and the audio equipment. It is investigated whether the system can truly reproduce the sound volume ratio of each frequency, that is, the signal amplification of each frequency is the same, an excellent sound reinforcement system , There should be no phenomenon that some frequencies are too strong and some frequencies are not enough. The main methods to obtain good transmission frequency characteristics are: reasonable sound design, pink noise spectrum analyzer method to adjust the equalizer, and the use of speakers with good frequency response characteristics to play.
24. Transmission line
The quality of the cables between the devices in the audio system will directly affect the sound quality and sound reproduction quality of the audio system. The influence of the transmission line on the sound signal is not limited to the direct current cathode. Due to the influence of the distribution parameters, skin effect, multi-core distortion and other factors, the accompanying eddy current loss and electromagnetic induction will have a certain destructive effect on the sound quality, resulting in different frequencies. When the signal passes through the wire, the cathodic reactance is not the same, and the amount of phase shift is also different. The influence of the transmission line on the sound signal depends on the conductor material (such as copper, oxygen-free copper, gold, aluminum, etc.), the wire geometry (such as wire diameter, number of strands, twisting method, outer insulation material of the wire) and wire technology Craftsmanship and many other aspects. On the premise of meeting the requirements of use, the transmission line should be as short as possible and in good contact with the equipment, and pay attention to shielding and anti-interference issues, and minimize the loss of sound signal (including the loss of amplitude, frequency and phase). Commonly used transmission lines have audio shielding Cable, digital cable, speaker cable, etc.
25, sub-frequency
Also known as super bass, generally refers to the bass frequency below 100 Hz. The sub-low frequency determines the fullness of the sound, making the bass long, deep, and powerful. This frequency has almost no sense of sound image localization, so the position change of the sub-low frequency speaker in the sound field has little effect on the sound image localization. The range of sub-low frequencies is the range of instruments such as double bass, bass drum, and organ, which can make the sound of these instruments perfect. When the sub-low frequency components in the audio are insufficient, the sound will not sound thick enough and a little too thin, but when the sub-low frequencies are too strong, the sound will be muddy.
26, mono
Like hearing the sound through the keyhole (keyhole effect), there is no sound like a group feeling, the sound is poor and tasteless, thin and superficial, even if multiple speakers play, because there are no differences in the sound, the sound will not be improved, with the help of different The difference in volume between sound sources will sound slightly different in depth.
2 mono recording
Multiple microphones respectively pick up the tones of a single instrument or grouped instruments and send them to the mixer. Then the picked up sounds are reasonably synthesized by the mixer and input to a monaural recorder for recording. For the early recording method, it is difficult to make major adjustments, processing and polishing of the recording effect, because once the characteristics, position and mixing ratio of each microphone are determined, the recording effect cannot basically be changed, and there is little room for later processing. In the process of monophonic recording, as long as one actor makes a mistake or enters noise, the entire program or one of the segments must be re-recorded, because the efficiency of monophonic recording is not high, the cost is high, and the quality cannot be guaranteed. .
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