What Does the Unit kHz Mean in Digital Audio?

kHz is short for kilohertz and is a measurement of frequency, or cycles per second. In digital audio, this measurement describes the number of data chunks used per second to represent an analog sound in digital form. These data chunks are known as the sampling rate or sampling frequency.

This definition is often confused with another popular term in digital audio, known as a bitrate (measured in kbps). However, the difference between these two terms is that bitrate measures how much data is sampled every second (size of the chunks) rather than the number of chunks (frequency).

Common Sampling Rates Used for Digital Music Content

In digital audio, the most common sampling rates you'll encounter include:

• 8 kHz for speech, audiobooks, and other spoken materials.
• 22 kHz for digitized analog mono recordings, such as vinyl records and cassette tapes.
• 32 kHz for streaming music and radio stations.
• 44.1 kHz for audio CDs and typically the de facto standard for downloaded music, including popular formats like MP3, AAC, WMA, WAV, and others.
• 48 and 96 kHz is used for high-definition equipment and professional audio.

Does kHz Determine Audio Quality?

In theory, the higher the kHz value is, the better the sound quality. This is due to more data chunks being used to describe the analog waveform. This is normally true in the case of digital music, which contains a complex mix of frequencies. However, this theory collapses when dealing with other types of analog sound, such as speech.

The popular sampling rate for speech is 8 kHz—below audio CD quality at 44.1 kHz. This is because the human voice has a frequency range of approximately 0.3 to 3 kHz. With this example in mind, a higher kHz doesn't always mean better quality audio.

What's more is that, as the frequency climbs to levels that most humans can't hear (usually around 20 kHz), those inaudible frequencies may nonetheless affect the sound quality.

You can test this by listening to something at an ultra-high frequency that your sound device supports but that you're not supposed to hear. You might find that, depending on your equipment, you'll hear clicks, whistles, and other sounds.

These sounds mean that the sampling rate is set too high. You can either buy different equipment that can support those frequencies or reduce the sampling rate to something more manageable, such as 44.1 kHz.