How to Find the Sample Rate and Bit Depth of an Audio File
How do you find out the sample rate again? I often forgot how to do it but actually there is an easy and quick way to find out the current sample rate and bit depth of any given audio file in any format within a few seconds. Here is how it goes:
- Open your audio file with the QuickTime player
- Open the Movie Inspector by clicking “Window>Show Movie Inspector” in the menu or simply by hitting ⌘+I ( Command I )
- Under format you see the current sample rate and bit depth of your audio file
What is a Sample Rate?
For those who wonder and want to find out more about sample and bit rate: The sample rate defines the number of samples per second of a digital audio file. A sample in digital audio is just a number but if draw a line connecting a great number of samples you would see a waveform. This digital waveform is a representation of an acoustical waveform that we could hear as sound.
The higher the sample rate, the more samples there are in one second. The more samples, the better the representation of the acoustical waveform and therefore the higher the audio quality. Typical sample rates are 44.1kHz, 48kHz, 96kHz and 192kHz. KHz stands for 1000 per second. With a sample rate of 44.1kHz an audio file consists of 44100 samples per second.
Sometimes, something strange happens. You open a session in your Digital Audio Workstation (DAW) with a sample rate of 44.1kHz but the audio file you are playing has a rate of 48kHz. As you play 44100 in place of 48000 sample per second your song gets longer and the pitch of it slightly drops. The other way round, when you play a 44.1kHz track in 48kHz the length of it gets shorter and the pitch higher. Be aware of it and change your settings accordingly.
What is Bit Depth?
In digital audio the bit depth describes how many bits are used for one sample. Similar to the sample rate it is safe to say how higher the bit depth how better the sound quality.
Thinking of a audio waveform again we can clearly see why that holds true. In order to represent the span between the highest and lowest point of a waveform in digital audio we create a equally distributed scale of numbers. The more numbers or bits we use for the scale the closer we can get to the actual amplitude. The closer we can get the smaller is the mistake we add to our audio signal. This mistake is called quantization noise.
Typically audio formats use a bit depth of 8bit, 16bit or 24bit.