Digital Audio Fundamentals

What is digital audio?

Digital audio refers to the representation of sound in a digital format, wherein audio signals are converted into a series of binary numbers that can be stored, transmitted, and manipulated by electronic devices such as computers and audio processors.

Unlike analog audio, represented by continuously varying electrical signals, digital audio breaks down sound into discrete samples at regular intervals, typically measured in thousands of samples per second (expressed as ). Each sample captures the amplitude of the audio waveform at a specific point in time, allowing for precise reproduction and manipulation of sound.

Digital audio has revolutionized how we record, edit, transmit, and reproduce sound, enabling unprecedented levels of fidelity, flexibility, and convenience in a wide range of applications, from music production and broadcasting to telecommunications and multimedia entertainment.

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Conversion process

Recording or converting sound into a digital format involves two primary steps: sampling and quantization.

Sampling

Sound is a continuous analog wave. To digitize this sound, it is sampled at discrete intervals. The sampling rate, measured in Hertz (Hz), defines how many times per second the sound is sampled. A common sampling rate for CD-quality audio is 44.1 kHz, meaning the audio is sampled 44,100 times per second.

In broadcast video production, the sample rate is 48 kHz; for high-quality audio recording and mastering, the sample rate can be up to 768 kHz.

Quantization

Once sampled, each snapshot of the sound's amplitude is converted into a digital value. This process is known as quantization. The bit depth determines the resolution of this conversion, with higher bit depths allowing a more precise representation of the sound's amplitude. Common bit depths include 16-bit, 24-bit, and 32-bit.

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Audio formats

In addition to the fundamental concepts of sampling and quantization, understanding digital audio involves familiarity with various audio file formats. These formats can be categorized into two main types: uncompressed and compressed.

Uncompressed Formats

These formats store digital audio data without any compression, preserving the original quality of the audio. Common uncompressed audio formats include:

WAV (Waveform Audio File Format): Developed by IBM and Microsoft, it's a standard format for storing audio on PCs.

AIFF (Audio Interchange File Format): Developed by Apple, similar in quality and structure to WAV, commonly used on Mac computers.

Compressed Formats

Compressed formats store audio data using algorithms that eliminate redundant or less audible information to reduce file size. Compressed formats can be lossless or lossy.

Lossless Formats: These compress audio data without losing any information, allowing the original audio to be perfectly reconstructed from the compressed data. Examples include FLAC (Free Lossless Audio Codec) and ALAC (Apple Lossless Audio Codec).

Lossy Formats: These formats achieve much higher compression rates by permanently removing some audio information based on psychoacoustic models that determine the least audible sounds. MP3 (MPEG Audio Layer III), AAC (Advanced Audio Coding), and Opus are widely used lossy formats.