You can often see terms such as ‘320 kbps' or ‘192 kbps' associated with various audio file formats, such as MP3. These indicate the ‘bit rate' of the audio file. But what exactly does that mean? In this article we spent 8 hours diving deep on the topic to explain everything you need to know – which is the best format to use for exporting? What are the sound differences? How to maximize quality and more. Scroll on to become a bit rate master!
What is Bit Rate and Why Does it Matter?
In digital audio, bit rate refers to the amount of data, more specifically, the number of bits encoded in an audio file in a single second. Audio files with higher bit rates contain more data, therefore they have better sound quality.
Bit rate is a term that gets used in both computing and telecommunication.
In telecommunication, for example in file-sharing or streaming, the bit rate conveys the speed of the data transfer. In multimedia, the bit rate is used to determine how much data is encoded in one second of a digital medium, such as audio or video.
More data means more detail, therefore, a higher bit rate provides better sound or image quality.
In digital audio, there are two major audio format types:
The main difference between these is the quality and the file size
Lossless file formats, such as WAV are uncompressed, meaning they do not lose any data during the encoding process, therefore they provide exceptional sound quality since they can accurately replicate all the tonal characteristics of the recorded sound.
In addition, there are lossless file formats such as FLAC, that are compressed, however, this is done in a way that does not lead to any data loss.
On the other hand, lossy formats, such as MP3, are heavily compressed, therefore they lose a significant amount of data during the encoding process, which leads to sound quality degradation.
A major advantage of lossy formats however is that they require significantly less storage space than lossless formats, for example, uncompressed WAV files. This makes them ideal for file sharing or streaming purposes. For this reason, the MP3 format played a significant role in the rise of music piracy.
As you might have already guessed, lossless audio files have higher bit rates, while lossy files have lower bit rates since they store fewer data per second.
The unit of measurement that we use for bit rate is bit per second (bit/s or bps). This can be converted into different formats, such as Mbit/s (megabit per second) or Gbit/s (gigabit per second). For audio, we use kilobit per second (kbit/s or kbps). It is important not to confuse kilobit per second with kilobyte per second (KBps)!
Can You Tell The Difference Between 64, 128, 192, 256 & 320kbps?
While it is more difficult to hear the difference between bit rates that are closer to each other, such as 256 and 320kbps, the difference between very low and high bit rates, for example, 64 and 1411 kbps, can be quite drastic and noticeable even for regular music consumers who do not possess advanced listening skills.
The higher the bit rate of an audio file is, the more information it will contain per second, which means that you will hear more detail as the fidelity increases. The instruments will sound clearer as there will be increased high-end, dynamic range and less distortion and artefacts.
A lower bit rate means less fidelity, and as you begin to approach the lowest bit rates, usually below and beyond 64 kbps, you will begin to recognize the characteristics that are often associated with lo-fi (low-fidelity) sound, such as lack of high frequencies, excessive mid-range, overcompression and distortion.
It goes without saying that those who have more advanced listening skills and regularly listen to high-fidelity audio, such as audio engineers and audiophiles, will notice the differences easier.
The general audience is not used to listening to high-resolution audio, as these days, the majority of people tend to consume music on streaming services like Spotify, which stream music at a lower bit rate, between 24 and 320 kbits/s.
Having said that, there are certain streaming platforms like Tidal, which offer subscription plans that allow the listener to stream music at higher bitrates, such as 1411 kbits/s or even 9217 kbit/s.
It is important to add that whether or not you can hear the difference between the different bit rates can also highly depend on the listening environment and the medium that you're using to listen to the audio.
For example, if you're listening to music with low-budget earphones or through the speakers of your phone, you will most likely not be able to notice a major difference, as these mediums tend to have very poor sound quality. On the other hand, if you're listening to music through high-quality studio monitors or studio headphones, the difference will be very noticeable.
Which MP3 Bit Rate is The Best To Use for Listening?
With lossy audio formats, you should always aim for the highest available bit rate. For MP3, this is 320 kbps. You could choose a lower bit rate, but the sound quality degradation will become very noticeable around 128 kbps. If you are an audiophile, you want to stick to lossless file formats and higher bit rates, specifically 1411.2 kbps and above.
You will be able to hear the differences in higher-end systems. If you're listening on apple earbuds it's likely you won't be able to tell.
It also depends on your data plan or storage on your device. You can store a lot more 128kbps MP3s on your device and you save a lot more data streaming these too. High quality comes at a cost, and if you're on your phone, you most likely won't be able to tell much of a difference.
Can I Use MP3 Files in My Productions?
It is not recommended to use MP3 files in your productions since it is a lossy format. In professional music production, we generally utilise lossless file formats, such as WAV or AIFF due to their superior audio quality.
In music production, we aim to utilise high-quality audio formats, so we can achieve the best sounding result. Lossless formats ensure that we are working with high-quality raw tracks from the beginning that accurately represent the original signal.
MP3 files already have compression applied to them, which creates a number of issues; they have less dynamic range, high frequencies, detail and they often distort. In other words, they already sound processed.
In music production, we want to work with good quality raw recordings, so we can apply our own processing to them later. If you add processing to an already processed track, you will not be able to achieve the same results.
Moreover, if you want to send your song to a professional audio engineer for mixing or mastering, they will not even accept MP3 files. To this day, the industry-standard file formats for music production are WAV and AIFF.
A lossless format can always be converted into a lossy format, however, the same cannot be done the other way around.
You can use MP3s in music production, but it's advisable to avoid this. With extra compression, you may need more dithering to avoid quantisation distortion.
How to Calculate Bit Rate?
In order to calculate the bit rate of an audio file, we have to use the following equation:
Sample rate x bit depth x the number of channels = Bit rate
To understand how bit rate is calculated, first, we have to know what sample rate and bit depth are.
Let's discuss sample rate first!
In order to play back the audio that we recorded with a computer, the incoming analogue signal has to be converted into digital data.
This is called analogue to digital conversion or ADC. After this, the digital data has to be converted back into an analogue signal that we can play the audio back on our speakers. This is called digital to analogue conversion or DAC.
It is the audio interface's job to take care of these processes, and using a digital audio interface can often cause issues with latency during the recording process.
In order to recreate the analogue signal, the interface's converter has to measure and take a myriad of snapshots, in other words, samples of the signal. The sample rate determines how many samples the converter takes in a single second and is measured with the unit Hertz (Hz).
A higher sample rate takes more samples, which provides a more accurate recreation of the analogue signal.
The sample rate for CD sound quality is 44.1 kHz. For many years, this was the standard in the recording industry, however, nowadays 48 kHz and even higher sample rates are becoming even more popular, mainly due to the rise of high-resolution music streaming and the declining popularity of the CD format.
In most DAWs, the default sample rate is 44.1 kHz and you should never use a sample rate that is lower than this.
The reason behind this lies in the human hearing range. The human ear can only hear sounds between 20 and 20 000 Hz (20kHz).
According to the Nyquist Theorem, in order to accurately recreate an analogue signal in digital form, the individual cycles of an analogue waveform have to be sampled at least at two different positions.
If this doesn't happen, the converter will not be able to recreate the waveform accurately, and it could mistake the frequency for an entirely different one. This is called aliasing. So, if we want to sample a frequency of 20 kHz, the sample rate has to be at least 40 kHz.
If you use a sample rate of 44.1 kHz instead of 40 kHz you can prevent aliasing from happening. Because, by increasing the sample rate, you minimise the chance of aliasing happening even more.
Very high sample rates, for instance, 192 kHz, are mainly utilized in sound design, especially when using effects, such as time stretching or pitch-shifting, which are done by playing back the samples at a slower speed.
These effects tend to produce lots of unpleasant artefacts, hence the use of a higher sample rate to produce a more natural sounding result.
Now let's talk about bit depth! The bit depth determines how many bits a single sample contains.
This is used to measure the dynamic range of the signal. In this context, dynamic range describes the difference between the noise floor and the loudest possible volume level that we can record before digital clipping occurs.
- 1 bit equals 6 dB of dynamic range.
- 16 bit equals 96 dB (16 x 6) of dynamic range.
- Nowadays, a bit depth of 24 bits per sample, which allows 144 dB of dynamic range, is the most commonly used bit depth.
Now that we know what sample rate and bit depth are, we can calculate the bit rate. Let's take the bit rate of a CD for example.
CD quality audio is always sampled at 44.1kHz and the bit depth is always 16 bit.
If either the sample rate is higher than 44.1kHz or the bit depth is above 16 bit, the audio is considered high-resolution audio.
Sample rate x bit depth x the number of channels = Bit rate
44.1kHz x 16 bit x 2 (Stereo=left and right channel) = 1411.2 kilobits per second.
As you can see, the bit rate of a CD quality audio file is 1411.2 kbps.
How to Use Bit Rate to Calculate the Size of an Audio File?
As mentioned earlier, audio files with lower bit rates require significantly less storage space than those with higher bit rates. If we know the bit rate of an audio file, we can also calculate the size of the file.
Let's compare the sizes of two audio files with lower and a higher bit rates:
Example 1: A 3 minute long MP3 file with a bit rate of 320 kbps
1 kilobit = 1000 bits
1 byte = 8 bits
1 kilobyte = 1000 bytes = 8000 bits = 8 kilobits
320 kilobits per second = 40 kilobytes per second
40 kilobytes x 3 minutes (180 seconds) = 7200 kilobytes = 7.2 megabytes
Example 2: 3 minutes of high-resolution audio, (96kHz, 24bit) with the bit rate of 4608 kbps
4608 kilobits per second = 576 kilobytes per second
576 kilobytes x 180 seconds = 103680 kilobytes = 103.68 megabytes
As you can see, the size of the high-resolution audio file is almost 14 and a half times larger than the size of the MP3 file.
Although this might not seem like a big deal, since we're only talking about megabytes, the size difference can be quite drastic if you want to export numerous high-resolution audio files. Furthermore, it can also greatly affect the speed of streaming, exporting and file sharing. This is the reason why many music streaming services utilize lower bit rates.
To sum up, in digital audio, bit rate is used to describe the amount of data encoded in each second of an audio file. Audio files with higher bit rates have better sound quality but require more storage space. Lossless audio formats like WAV are uncompressed and have higher bit rates, while lossy formats, such as MP3, are heavily compressed and have a lower bit rate, therefore, they have inferior sound quality.
It's okay to use lossy formats for listening and file-sharing purposes, however, in your productions, you should only work with lossless formats like WAV.
If you liked this article and would like to learn more, make sure to check out our other articles as well, as we cover a wide range of topics!