An Introduction to Audio and Its Main Features & Formats [MiniTool Wiki]

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About Audio

Audio has multiple meanings. It can refer to a detailed description of a compressed digital sound format released by Sun Micosystems company, which is a frequently used sound file format in Internet. The LiveAudio in Netscape Navigatir browsers supports Audio format sound files. In MiniTool, you are able to edit your audio for video quickly.

Audio, the frequency of the voice of a person speaking, usually refers to the frequency ranging from 300Hz to 3400Hz. In some aspects it can be referred to as vibration of a wave filter. Today, you can get audio books easily.

audio

As a professional term, audio refers to all sounds that human can hear even including noise. After the sound is recorded – whether it is talking, singing or musical instruments, it can be processed by digital music software.

Even though making the recorded sound into a CD, all the sounds have not changed at this time because the CD itself is an audio file type. The audio is just the sound stored in the computer.

If you have a computer and a corresponding audio recorder or audio card, you can record all the sounds. The acoustic characteristic of the sound can be stored in the form of computer hard disk files.

On the contrary, the stored audio files can be played in a certain audio program to restore the previously recorded sound. 

Main Features of Audio

Playing or processing audio files in a computer is equals to perform digital-to-analog conversions on the audio files. The process is also composed of sampling and quantization. The lowest frequency that can be heard by the human ear is from 20Hz to the highest frequency of 20KHZ.

Therefore, the maximum bandwidth of audio is 20KHZ, so the sampling rate needs to be between 40-50KHZ. Moreover, more quantization bits are needed for each sample.

The standard for audio digitization is a signal-to-noise ratio of 16-96 db per sample. The PCM is modulated by linear pulse coding, and each quantization step has an equal length. This standard is used in the production of audio files.

Main Audio Formats

Just as images have multiple file formats, audio files come in many formats. Main audio formats include CD, WAV, MP3, MIDI, WMA, RealAudio, VQF, OGF.

CD: If you see the *.cda format when opening most playback software, this is CD audio track. However, the *.cda file is just an index message for it doesn’t contain sound information. Therefore, regardless of the length of the CD music, the *.cda file seen on the computer is 44 bytes long.

Tip: You cannot directly copy the *.cda file in CD format to the hard disk. Instead, you need to use the capture track software like EAC to convert the CD format file into WAV.

WAV: It is a sound file format developed by Microsoft conforming to the PIFF Resource Interchange File Format standard. It is used to store audio information resources on Windows platform and supported by Windows platform and other applications.

WAV supports MSADPCM, CCITTALAW and other compression methods, as well as multiple audio digits. The sampling frequency, channel, speed and quantization bit of WAV are the same as that of CD. Naturally, the sound file quality of WAV is similar to that of CD, and it is also a popular sound file format on PC.

MP3: It refers to the audio section in MPEG standard, MPEG audio layer. According to the compression quality and code processing, the audio is divided into three layers (*.mp1, *.mp2 and *.mp3).

MP3 audio file compression is a lossy compression – MP3 audio encoding has a high compression ratio of 10:1 to 12:1, while basically keeping the low audio part undistorted, but sacrificing the 12KHZ to 16KHGZ high audio part of the sound file.

The quality is in exchange for the size of the file. Music files of the same length are stored in *.mp3 format generally occupying 1/10 of *.wav files, but the sound quality is not as good as CD or WAV sound files format.

WMA: The sound quality of WMA format is better than that of MP3 and far better than that of RA format. It achieves higher compression ratio than MP3 by reducing the data traffic but maintaining sound quality.  

Another advantage of WMA is that content providers can add copy protection through DRM (Digital Rights Management) solutions such as Windows Media Rights Manager 7.

If an audio file cannot be opened in a certain audio format, you may need an audio converter to convert.

Versions above Windows Media Player 7.0 add converting the CD to WMA sound format feature. In Window XP operating system, WMA is the code format by default. The WMA format can adjust the sound quality when recording.

When you lost your audio files due to virus attack, hard drive failure or other causes, it is strongly recommended to use MiniTool Photo Recovery to find them back. Audio formats like WAV, MP3 mentioned above are able to be recovered by the software.

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