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Pitch is that aspect of sound characterized by a high thin sound quality or low rumbling sound quality. Pitch is measured by the frequency of sound vibrations that occur over time. Low sounds have few vibrations per second, high sounds have many vibrations per second. This number of vibrations is referred to as the frequency and is measured in a value called Hertz (Hz). The range of frequencies that humans can hear is from 20 to 20,000Hz. To put this into perspective, the lowest human voices can produce about 88 Hz for a bass voice and about 1,100 Hz for a soprano voice. A piano will generate about 27 Hz at its lowest note and about 4100Hz at its highest note. Humans can hear a limited range of sound pitch, from very high sounds to very low sounds. Human hearing is also not consistent across the range of frequencies. People tend to be more sensitive to some frequencies and less sensitive to others. Most commonly people have greater difficulty hearing sound in the lower frequencies.
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Sound loudness is measured in units called Decibels. 0 dB: threshold of sound and human hearing 20 dB: quiet room 30 dB: quiet conversation 40 dB: normal conversation 50 dB: loud conversation 70 dB: Busy street 110 dB: Power saw 120 dB: Threshold of pain 130 dB: Some concerts hit this level on occasion Like our sensitivity to pitch, human hearing is not consistently sensitive to loudness across the entire loudness spectrum. Human hearing is also subject to damage from exposure to sounds that are too loud. While your hearing can usually recover from temporary damage caused by sudden or brief loud sounds, continuous loud sound can cause permanent damage if you are exposed to it long enough. Your hearing cannot recover from this kind of damage. Human hearing naturally degenerates with age.
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Loudness Indicator: VU (Volume Unit) Meter On sound equipment such as audio mixers, loudness is displayed on a VU meter. Two common display types are the scale and needle, and the lighted (LED) indicators. For recording sound at its Optimum VU level, the sound level should read about 85% to 100%. Optimal is also referred to as “Zero” VU.
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The sound that you will be recording can be though of as being in two main categories: target sound, which comes from the person’s voice you are recording or the object you are recording, and ambient sound, which is sound emanating from the surrounding environment, (also called natural sound or room tone). Ambient sound can be extremely important in helping listeners understand the location or setting in which a recording was made. But when it is too noticeable, it makes the subject or target sound difficult to hear. So when ambient sound is heard along with target sound, it should not overpower or distract from the subject or target sound. Ambient sound needs to be carefully blended with the subject or target sound so the listener does not have to struggle to hear the target sound. In sound production situations, the sound operator will record the target sound so it stands out from the ambient sound. This is done by using proper microphone placement (more on this later). Sometimes the sound operator will record additional ambient sound as a separate recording, without the target sound (subjects speaking). This way, the sound editor can mix subject and ambient together separately and with greater control during the post-production phase of the project.
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Noise is any kind of sound that is unwanted. It can emanate from the recording equipment itself or from the way the equipment is used during the recording process, or even the environment. For example, a microphone that is placed too far away from the target sound source might record so much ambient sound along with the target sound, that the target sound cannot be distinguished from the ambient sound. When that happens, the ambient sound might make it difficult to hear the target sound easily. In this case, the unwanted ambient sound would be considered noise. The relationship between the target sound and the unwanted sound is called the signal-to-noise ratio. The word signal here means the target sound.
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Signal-to-Noise Ratio (S/N RATIO) The word signal here means the target sound. This ratio represents the difference in loudness between the target (desired) sound and the unwanted or ambient sound. When the sound level of your subject is recorded at optimum level, the ambient sound may be so low in comparison that becomes unnoticeable, or just noticeable enough to help create the mood of the piece. This is good. Remember that there are occasions when a small amount of ambient sound is desirable because it helps provide context or set the mood of the recording. However, if the listener has to struggle to hear your subject, you can assume the background sound is probably too loud.
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A desirable audio level strength on a VU meter will measure about 80% to 100%, while the ambient sound will be very low, perhaps 5-10%. Depicted here is a high or good signal-to-noise ratio.
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In contrast, when the subject sound is about the same as the background noise, it will be difficult to distinguish the two, which makes it difficult for listeners to comprehend the message. | 
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During the post-production stages of a project it is possible to amplify sound levels that were originally recorded too low. But if the signal-to-noise ratio was low in the original recording, amplification will do nothing more than make the entire sound package (target sound and ambient sound) louder. It will not separate the target sound from the ambient sound and there will be no resulting benefit.
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The best practice is to make sure you are recording subject or target sound at optimum VU level when you make the original recording, and that ambient levels are minimal during the original sound recording.
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You can achieve a good signal-to-noise ratio by placing the microphone appropriately in relation to the target or subject. Most microphones are designed to pick up sound best when placed about one hand’s width away from the sound source. And if the sound is coming from someone’s voice, and you are using a microphone in front of that person’s voice, then place microphone about 45degrees off center to avoid possibility of popping sounds when words hard syllables are spoken. (Popping P’s) Some microphones are designed to be used up close, about an inch away from the sound source. These mics are characterized by a large windscreen. When using lapel mics, Popping P’s are not so much of a problem, because the mic will be below the subject’s mouth. But be sure to keep the mic paced close to the neckline, not down in the middle of the chest. This will give you a better signal-to-noise ratio.
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The physical design characteristics of microphones vary. The hand-held mic has a metal shaft, a heavy windscreen, and is the most rugged design. It is ideal for stage performers, and reporters in the field who have to maintain close control over the distance of the mic to the subject. For example, in situations where there is a lot of loud ambient sound (basketball game or on a busy street), you will often see the reporter hold the mic fairly close to a subject’s mouth (slightly less than a hand’s with away but off to the side a bit) to increase the signal-to-noise or subject-to-ambient sound ratio. The clip on mic attaches to clothing with a clip and is highly sensitive to sound from all sides. It is ideal for indoor use. When used outdoors, however, it often needs a wind screen to soften ambient sound and noise from wind. The shotgun mic typically has a long shaft and is designed for picking up sound anywhere from a few inches to a few feet away from the sound source. This type of mic is used often with actors in a movie, with the mic mounted on a boom arm and held just out of the picture frame over or under the actors’ heads.
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Cardioid microphones have an inverted heart-shaped pick-up pattern which makes them more sensitive to sound out in front of the mic than from the side and rear. The hypercardioid (shotgun) is even more like this. The omnidirectional is sensitive to sounds from all directions, and bi-directional patterns are often found in stereo mics.
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Sound over-modulation occurs sound is too loud for the equipment in use. If the mic it too close to the source and the source is too loud, the resulting sound will be distorted. Distortion can also occur within sound equipment such as audio mixers, when the sound level of a channel is turned up too high. Over-modulated sound may not necessarily sound loud to the ear, but it will likely appear at the highest levels on the VU meter or even off the VU scale. The resulting sound will have a buzzing or crackling character, regardless of how loud it sounds to the ear. Sound that is originally recorded as over-modulation cannot be repaired. It simply makes the sound recording unusable and must be avoided. Always do a test recording and playback through your headset to ensure that your sound recording will not be over-modulated. Always re-record those sections of your recording that are over-modulated. A pop filter on the microphone is sometimes lessen the possibility of popping sounds in microphones but will do little to cut down over-modulation.
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A way to control the tone quality of sound is through Equalization, sometimes called “EQ.” It is a type of sound manipulation that emphasizes or de-emphasizes the loudness of certain frequencies (pitch) of a signal. This is the same feature that is found on many audio mixers and radios often called Tone Control, allowing you to boost or lessen the treble, midrange, or bass sounds. Equalization is a useful tool, but it has limitations. Sometimes the goal of applying EQ is to attempt to remove an annoying low level rumble or high pitched hiss that was recorded with the original sound. While it is true this can be done, if you remove a portion of the sound frequency that contains the unwanted sound, you also remove any of the subject or target sound that was present at that frequency as well. If target sound is mixed with noise in the original recording, for all practical purposes, they cannot be separated afterward. By using EQ, you may lessen the effect to some extent.
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Setting the Record-level of a recording device through the use of an audio mixer can sometimes be done manually so as to keep the sound at optimum. But many audio recording devices also have a feature called ACG, or automatic gain (volume) control, which allows the sound levels from the microphone/s to be automatically kept at optimum VU level. This feature is excellent in situations in which the operator cannot pay close attention to manually modulating incoming sound levels.
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The major shortcoming of ACG for audio occurs during periods of silence. With the AGC switched on, when the subject or target sound stops momentarily and there is a period of silence, the AGC continues to adjust itself upward in the absence of sound. This results in the slow rising of ambient or background sound, which may be unwanted. Then, once the subject begins to speak again, there is a moment of sound over-modulation because the AGC has boosted the record level so high and then must readjust quickly downward. This often results in a poor recording. When you expect that there will be periods of silence for more than several seconds at a time, it is sometimes better to set the level manually to the estimated sound level and not use the AGC.
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This is a process in which you match the RECORD level on the recording unit to the optimum VU output of a source device. For audio, this is usually done using a steady reference sound called TONE (1000Hz) playing it at full VU. As it plays, you adjust the RECORD level on the recording device upward to match full VU. When the source is playing at full VU and the Recording unit is recording at full VU, then the two are calibrated.
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Different audio equipment renders different audio quality. When a production involves different locations and equipment setups, it is recommended that you use the same kind of equipment throughout an entire production, including the same kind of mics.
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The place on a recording device where a sound source enters the unit is called the INPUT. Most units have two types of INPUTS: Mic-level and Line-level. The place on a unit where the sound signal leaves the unit is called the OUTPUT. There are two types of audio OUTPUTS. The amplified output is labeled as Speakers usually. The Line out output is used to connect to either a PA system (an amplifier and speakers), or something that has a built-in amplifier and speakers of its own, such as a monitor or TV set.
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Sound from audio equipment is commonly categorized into two levels of amplification: mic-level and line-level. Line-level sound is already pre-amplified and has a comparatively powerful signal. Line level output comes from items such as CDs, VCRs, DVD’s MP3 players and is found on the output connecters usually labeled LINE OUT or AUDIO OUT. In contrast, the microphone audio output level has much less amplification. On devices that accept a microphone, look for the input labeled MIC IN. Do not put LINE OUT signals into MIC IN. The resulting sound will be too loud and distorted. Conversely, do not connect a microphone to LINE IN on a recording device, because the audio coming from the mic will be too weak.
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This means that distant sounds go with distant objects and close up sounds go with close up objects.
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Professional-grade audio cables are used for high quality audio, usually on microphones and on professional-grade equipment components. The cable has two twisted conductors (pos., neg.) surrounded by braided shield to stop interference. The connectors have three pins and are called XLR connectors. The connectors push together and snap-lock, and release and pull apart with the press of a release tab. |
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RCA connectors Consumer-grade cables have one center conductor surrounded by a braided shield to stop interference. These use the RCA connector. These are common in consumer-grade equipment components. They are used for both audio and video, but not microphone connections.
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Mini (1/8”) connectors Consumer-grade cables also use the mini-connector (1/8th inch) connector. This connector is usually used for headsets and consumer-grade microphone connectors.
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