Audio Files

Properties of Digital Audio Files

When sound is recorded digitally, it is converted from a continuous wave (the way sound actually travels through the air) into a series of numerical measurements stored as data. Two properties control how accurately that conversion captures the original sound: sample rate and bit depth.

Sample Rate

Sample rate is the number of times per second that the audio is measured (or "sampled") during recording. It is expressed in hertz (Hz) or kilohertz (kHz). A sample rate of 44,100 Hz — written as 44.1 kHz — means the audio is sampled 44,100 times every second. This is the standard for CD-quality audio.

A higher sample rate captures a wider range of frequencies, resulting in audio that more closely resembles the original sound. A lower sample rate misses detail, particularly at higher pitches, and can make audio sound muffled or distorted. For context, the human ear can detect frequencies up to approximately 20 kHz, which is why 44.1 kHz is considered sufficient for most listening purposes.

Bit Depth

Bit depth describes how much information is stored in each individual sample. It is measured in bits — typically 8-bit, 16-bit, or 24-bit. Think of each sample as a photograph of the sound at a single instant: bit depth determines how much detail that photograph can hold.

A higher bit depth means each sample captures a more precise measurement of the sound wave, resulting in a greater dynamic range — the difference between the quietest and loudest parts of the audio. 16-bit is standard for CDs and most digital distribution; 24-bit is used in professional recording studios where maximum precision is essential.

Low bit depth produces audio with a narrow dynamic range and introduces a hissing background noise called quantisation noise, which becomes audible in quiet passages.