Modern digital sound is the result of decades of advancement in the technology of recording and transmitting audio information. In 1937, Alec Reeves, a British inventor, filed a patent application for an “electrical signaling system” that could convert sound into a series of pulses to be transmitted over a line and later decoded. This idea was one of the foundations for the development of digital audio technology.
Since then, audio technology has come a long way; from Moog synthesizers and compact discs to VoIP calls and music streaming services. Today many streaming services offer high-quality audio options and even lossless formats - a capability made far more accessible than before thanks to increased internet speeds and storage capacity.
What exactly is bitrate?
Bitrate, simply put, is the amount of data used to represent or transmit an audio file per second, and is usually expressed in the unit “kilobits per second” or kbps. In general, the more data available per second to represent the sound, the more detail of the audio signal can be captured; of course, this relationship also depends on the file type and the compression method.
To calculate the raw bitrate of a digital audio file, three main factors are considered: sample rate, bit depth, and number of channels.
The sample rate, measured in hertz, specifies how many times per second the audio signal is sampled. Bit depth indicates the number of bits allocated to record each sample. By multiplying these two values by the number of audio channels, the raw bitrate can be calculated.
For example, standard CD audio with 16-bit depth and a 44.1 kHz sample rate, in two-channel stereo, has a bitrate of about 1411 kilobits per second.
The role of compression in sound quality
Another important part of the story concerns compression of audio files. Lossless files such as FLAC can reduce data size without removing the original audio information. In contrast, lossy formats like MP3 and AAC reduce file size by removing some of the audio information.
For this reason, simply comparing the bitrates of two files is not always sufficient to determine their quality. The codec type and compression method also matter, and a file compressed with a different format may perform differently at a given bitrate.
Is higher bitrate always better?
The short answer is no. The human ear’s ability to hear frequencies is also limited. The upper range of human hearing is typically considered to be around 20 kHz, and this range can decrease with age. Therefore, increasing the sample rate excessively does not necessarily create details that the human ear can hear.
Bit depth also affects dynamic range and the amount of detail that can be recorded at different loudness levels. Each bit adds roughly 6 dB to the dynamic range. As a result, a 24-bit file can theoretically have a much wider dynamic range than a 16-bit file.
However, using the full extent of that range implies listening at very high volume levels, which can be dangerous for hearing. Under normal music listening conditions, therefore, increasing bitrate or bit depth does not always mean a better listening experience.
Ultimately, sound quality is the combined result of sample rate, bit depth, number of channels, codec type, and amount of compression. For this reason, when choosing music streaming quality, one should not just look at the largest bitrate number; rather, one should see in which format and with what specifications that number is offered.