How does bit rate affect audio quality?

In 1937, British inventor Alec Reeves filed a patent application for an “electrical signaling system” capable of transcoding sound into pulses to be transmitted over a line for later decoding. That’s how digital audio was born – and boy, have we come a long way since then. Moog synthesizers, compact discs, and talk of early VoIP (voice over Internet protocol) clients have given way to crisper, cleaner sound everywhere you go. Music streaming platforms sell subscribers in high-resolution and lossless audio, with many offering the best audio quality you can get on the Internet.

Anything we can measure requires a good unit, and in the digital world we have bitrate: how many 0s and 1s we can transport over time. In theory, the more bits you can move per second, the more sound you can reproduce. Depending on how you group this information, higher bitrates give way to lower sounds, higher frequencies, or both. These two factors determine the clarity and breadth of your music.

For music, artists and producers typically record, export, and transport mastered songs at very high bandwidths. Distributors then economize on this downstream bandwidth to adapt it to their medium of choice: some remember compact discs offering great sound for their time, but they also had limited capacity. With fast internet and streaming media these days, we’ve come to a point where you can decide how much data you want to use to listen to “Mary Had A Little Lamb.” What? We don’t judge.

There are three factors that go into calculating the bit rate of a digital audio file: sample rate, bit depth, and the number of channels in the file. Sampling rate, measured in Hertz, describes the number of samples of an original sound that have been transcoded in a given second. Bit depth refers to the number of bits each sample is composed of. To find the bitrate, multiply the sample rate, bit depth, and number of channels together. For example, typical CD quality audio is quantized to 16 bits at 44.1 kHz. With two-channel stereo sound, the total bit rate is approximately 1411 kbps.

Many audio files will also have some level of compression. High resolution files will use lossless formats like FLAC which allow decompression while retaining all data in the file. Lossy formats like MP3 or AAC erase data from the file to reduce its size.

So, do you need the highest bitrate possible to enjoy all your music? Not really. The maximum frequency that human ears respond to is in the 20kHz range, and this number decreases with age and wear, so you shouldn’t worry too much about very high sampling rates. In terms of bit depth, each bit gives about 6 decibels of sound resolution; louder and the captured sound becomes distorted. The average human can perceive up to 130 dB, so you theoretically have the opportunity to experience a fuller range of sound with individual loudness on a 24-bit track compared to a 16-bit track. This could damage your hearing, and you probably won’t be listening at this proportional sound level anyway, so some loss of detail is expected.