Sound Fundamentals: Digital Audio, Formats, and Production
Understanding Sound
What is Sound?
From a physical point of view, sound is a vibration that propagates in an elastic medium, whether solid, liquid, or gas. When referring to audible sound for the human ear, it is defined as a sensation received by the auditory organ, produced by vibrations propagating through an elastic medium in the form of waves.
Requirements for Sound Production
To produce sound, the following are needed:
- An issuer or vibrating body.
- An elastic medium (transmitter of these vibrations).
- A receiver that captures these vibrations.
Digital Sound Concepts
Digital Sound Explained
Digital sound is more complex than analog sound because it does not store oscillations or waves directly. Instead, it uses a digital language of zeros and ones to represent the intensity or amplitude of sound over a period of time. Sound quality depends on the sampling frequency and resolution.
Sampling Frequency
Sampling frequency refers to the number of measurements taken per second. The higher the number of samples, the better the sound quality.
Resolution in Digital Audio
Resolution is the accuracy of the measured amplitude. It is measured in bits.
The Sampling Process
Sampling involves capturing an electrical signal at very short, regular intervals. This rate is known as the sampling rate. The frequency at which these measurements are made determines the sampling speed. This process involves:
Frequency in Sampling
Frequency: In the context of sampling, this refers to how accurately the original wave can be reconstructed from the sampled data.
Precision in Digital Audio
Precision: The quality and richness of playback are related to the accuracy with which the amplitude is measured, resulting in coded data.
Audio Compression
Compression is essential for the efficient transmission and storage of sound data. Any information ultimately becomes a sequence of zeros and ones. Encoding, performed in a specific order, reduces the size of the file content. Decoding restores the original data.
Sound Storage and Reproduction
Methods of Sound Storage
The storage and reproduction of sound can be achieved through various methods, historically including analog recording (like tape) and symbolic representation (like a musical score). While tape stores the actual waveform, a musical score contains information that informs the musician about the desired musical outcome.
Electronic Musical Scores
Modern systems often use electronic scores, which employ a language understood by musicians (similar to traditional notation) to store information for each sound source. An electronic score indicates when a note should sound, its tempo, volume, and how it should be played.
Popular Audio Formats
Common Audio Formats
- MIDI: 21KB
- WAV: 5.3MB
- MP3: 440KB
- RA (Real Audio): 850KB
- VQF: 280KB
MP3: A Closer Look
MP3 was launched in 1995; its successor is MP4, which offers even higher compression ratios (e.g., 40:1). MP3’s combination of good sound quality and small file size made it very popular on the internet. Its compression is based on psychoacoustics, focusing on what the human ear can actually perceive. These are very small files with minimal perceived loss of sound quality.
Using this format can reduce the size of a track from a CD by a factor of 12:1, and what’s more important, its quality is not significantly lost; even a 24:1 compression ratio can be acceptable. The most common use is for music storage, which typically involves ripping a CD to the computer’s hard drive and then converting it to this format using a ripper program. Higher bitrates (specified in Kbps) result in higher quality. You can also choose between stereo or mono, and the quality depends on the original WAV file you are working with. The main disadvantage is that you need a powerful machine, as it uses processor resources and needs to be decompressed for playback.
Sound Editing and Conversion Software
Audio Software
- Digital Audio Converter
- Audacity
- Mp3splt 0.5.7a