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Audio
Sound travels in the form of sound waves, and every sound that is transmitted begins and ends its life as a wave. The original sound recording and storage equipment was analog, meaning it stored audio information in a continuous wave-like manner. As technology progressed however, analog formats gave way to digital ones. The most visible example of this transformation was from records and tapes to CDs. Digital audio recordings store a representation of a sound wave in a form that can read and processed by a computer. Digital audio can be easily manipulated in a myriad of ways, it can be duplicated flawlessly, it can be compressed efficiently, it can be encrypted, and it can be easily transported over a network. For these and many other reasons, digital audio has dramatically changed the audio landscape.
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Microphones
Recording Audio
The basic properties of a good recording depend on the kind of recording being performed. For the most part, a recording with a fair dynamic range—low background noise and clear, audible audio of the subject—is desired, be it a speaker or frog calls. The basics to remember are selecting a good location, using the appropriate equipment and microphone, and getting good recording levels.
Selecting a Good Location
As in real estate, think location, location, location. If it is possible to control where you make recordings, try to find a location with low noise levels and a lockable door so people can't walk in.
Computers, air conditioning, and fans, with their low level hum, are enemies of a good recording. Short of access to a sound studio, you can alleviate problems with ambient noise by using an appropriate microphone or when editing.
Using the Appropriate Microphone
When buying a stereo, they say the most important component is the speakers, because they physically reproduce the sound. For recording audio, the most important component is the microphone, because it determines what the audio sounds like when it is recorded.
Omni |
Because the simplest design allows a device to pick up all sound, regardless of its point of origin, it is known as an omni-directional microphone. It is very easy to use and generally has good to outstanding frequency response. |
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Cardioid |
This design is a popular choice for sound reinforcement or recording lectures where class noise may be a problem. The concept is great: a microphone that picks up sounds from where it is pointed. The reality is different. Sounds from the back are merely reduced, not completely rejected, to the surprise of novice users. And the microphone will emphasize the low frequency components of any source that is very close to the diaphragm. This is known as the proximity effect, and many singers and radio announcers rely on it to add depth or chest to a basically light voice. |
Shotgun |
To exaggerate the directionality of cardioid microphones, the shotgun is extremely sensitive along the main axis, but it possesses pronounced extra lobes that vary considerably with frequency. In fact, the frequency response of this microphone is so bad that it is usually electronically restricted to the voice range, where it is used to record dialogue for film and video |
Lavaliere |
The lavaliere (or lav) microphone is commonly used with wireless systems so a speaker can move freely without being tied to a microphone stand or podium. The pickup range is small and the microphone is usually clipped to a shirt or lapel. |
Different Media Formats and Choices
Some of the common choices available to most faculty and staff are tape decks, mini disc recorders, video cameras (audio can still be recorded to a video tape even if the video is not going to be used), and recording directly to a computer.
Audio Tape: Everyone knows how to use a tape deck—push record. In addition, most higher-end tape decks allow monitoring of the recording, both with a set of headphones and level meters. The disadvantages are that audio tape is not especially sturdy, degrades over time as it is played, and has background hiss.
MP3 Player / Recorder: With digital formats becoming more popular, certain mp3 players have the capability to record audio directly into a digital audio format. These devices are small and reliable, and they can store considerable amounts of audio without the need to switch tapes. Some models can store upwards of 5 hours of audio to a .wav or .mp3 format—ideal if the audio is to be used on a computer, because it need not be captured on the computer in real time, saving time. However, high-end mp3 recorders are expensive, and their internal hard drives may stop working after extreme shock.
Mini Disc: Mini-disc recorders and discs are compact, easily portable, sturdy, and high quality. Using mini disc recorder for lectures or interviews with an appropriate microphone attachment works well. One disadvantage is that recordable mini discs are somewhat harder to find than audio tapes. A second disadvantage is that the audio recorded to a mini disc is compressed in order to fit on the smaller media. For some audio recording purposes in which the audio has to be analyzed scientifically for certain frequencies, the mini disc recorder is not appropriate, because the compression artificially degrades the audio signal.
Videotape: Often overlooked as a somewhat more common resource for audio recording are video cameras. While not designed specifically for audio recording, they nonetheless can record good audio, given an appropriate microphone attachment. The disadvantage is that it is not possible to monitor the recording with some consumer video cameras, to tell whether the signal is too soft or too loud. The only way to address this problem is to make a short test recording to play back with headphones connected to the camera to tell if acceptable audio levels are being captured.
Recording to a Computer
The advantage of recording directly to a computer is that there are no intermediary media to deal with, saving time. This would be a choice with a laptop or a controlled location such as a sound studio. One disadvantage is often the computer itself. The fan creates background noise, and often the microphones that come with a computer are extremely low end. At the very least, try to find a good microphone if you’re recording directly to a computer. The other disadvantage is possibly not knowing how to use the software required to record the files to a computer, whereas with a tape deck, most people know how to push record.
Many computers use a specially designed sound card to capture and play back audio. More recently, USB and Firewire audio interfaces have become more common, allowing connection of higher-quality microphones. In addition, special higher-quality microphones are designed to connect directly via USB, without the need for an additional audio interface or audio mixer.
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University of Wisconsin - Madison | Division of Information Technology
