The Basics of Audio: Sampling Rate, Bit Depth, and Bitrate

Introduction

Audio, as the name suggests, refers to “sound.” In the digital world, sound information is stored as audio files. There are various formats for audio files, such as WAV, AIFF, FLAC, ALAC, MP3, and AAC.

Audio Basics

AD Conversion (Analog to Digital Conversion)

The process of converting and saving analog sound to digital format is called sampling or AD conversion. When converting to digital format, the analog waveform is read and replaced with 0s and 1s.

DA Conversion (Digital to Analog Conversion)

To listen to digital audio, it needs to be converted back to analog format. This process is called DA conversion. The sound you hear from speakers or headphones is the sound converted from digital to analog.

What is Sampling Rate?

Sampling rate is the number of times per second that an analog signal is converted (sampled) to digital data. The unit used is Hz (Hertz). The CD format has a sampling rate of 44.1kHz, which means it samples the audio 44,100 times per second.

What is Bit Depth?

Bit depth represents the number of levels used to reproduce the sound volume from silence to maximum volume. The CD format uses 16 bits, which means it can represent 65,536 levels of volume difference. The higher the bit depth, the more precisely the volume can be represented.

The Difference Between 16-bit and 24-bit

The difference between 16-bit and 24-bit may not be noticeable for loud music, but it can be perceived for very quiet sounds. 24-bit can represent small volume changes more precisely than 16-bit.

The Relationship Between Bit Depth and Dynamic Range

The human ear is said to have the ability to hear a dynamic range of 120dB. 16-bit can represent a dynamic range of 96dB, while 24-bit can represent 144dB. For music with drastic volume differences, such as classical music, 24-bit is more suitable.

Calculating Bitrate

Bitrate can be calculated by multiplying the sampling rate by the bit depth and the number of channels. The bitrate of a CD-format WAV file is 1411.2kbps.

The Present and Future of Audio

Currently, 96kHz/24-bit audio is popular in the DTM (Desktop Music) world. While this provides very high sound quality, it also has the disadvantage of larger file sizes. Depending on the music genre, 44.1kHz/16-bit may be sufficient.