Let’s talk about the geeky world of audio digital conversion and how it impacts on music. Your music!
Sample rate is the amount of times that a sound is sampled per second. In the digital audio world the higher the sample rate the higher resolution of the audio signal. The problem is that the higher the sample rate – the larger each audio file. This starts to impact on hard drive space and processing power. In our Sydney recording studio we recently recorded a small album at the sample rate of 176.4kHz. In this article we are going to try and explain sample rates in music recording.
The relationship between an analogue signal and a sampled signal.[/caption] The lowest sample rate that you are likely to see being used in a recording studio is 44.1kHz. The “k” stands for ‘kilo’, which means ‘1000’. So this number means 44.1 times 1000. When this is expanded to integer (whole number) form this number will be 44100. Simple!
So what is the ‘Hz’? The Hz is the unit for frequency. Frequency is the number of times something happens within a period of time. In physic, and the other fields of science, we use the interval of one second when dealing with frequency. The ‘Hz’ is essentially ‘how many times something happens in one second’. That can be written as 1/s. So in the case of a 44.1kHz sample rate we know that the sound is being sampled at 44100 times per second! For brevity we just right 44.1kHz.
This is really fast, but it’s not the fastest. The next sample rate that you’ll see being used is 48kHz. This is more often used in big studios that deal with movies and TV. 48kHz was more closely related to film frame rate where 24 frames per second were being used in cinema. This rate was doubled and it was 48. If audio were being processed inside the and then being pressed straight to a CD (which accepts 44.1kHz) then 48kHz would not be the ideal format. The reason for this is the conversion that occurs when going from 48 – 44.1. The 48 kHz samples literally need to have their position recalculated so fit into the 44.1kHz sample. Rate it is this conversion that creates a quality loss. It’s not dramatic, but purists wouldn’t be happen with the quality impact of the recalculation.
So this brings us to 88.2kHz. This is the next sample rate up from 48kHz. This is a high sample rate and each file will be exactly twice the size of a 44.1kHz equivalent. However, due to the fact that there is an integer relationship between 88.2 and 44.1 there is no recalculation of position that goes on. Instead, every second sample is removed. Whilst the resolution is decreased to fit on to a CD, there is no quality loss from recalculation of sample position.
Therefore, there must be some integer equivalent to 48kHz, right? Yep, you guessed it! 96kHz! This sample rate is a higher resolution, yet again. If your final sample rate were to be down sized to 48kHz then 96kHz would be your choice of sample rate to record at in the studio. The same reason applies as is explained above.
We can go higher still!!! Next we go to double 88.2kHz, which is 176.4kHz. This is a very high sample rate and is rarely used in commercial recording studios. The next step is double 96kHz, which is 192kHz. You’ll start to notice the clarity in the top end of the signal at this rate. Also, you may not notice the benefits of using a higher sample rate when recording a single instrument, voice or sonic element. However, it becomes very noticeable when other elements start to get added into the mix. All of a sudden the clarity of each instruments remains more constant and separated than it would in a lower sample rate. Mixing becomes easier and more of a pleasure. It does strain the computer much more that if each file were lower in sample rate
So, 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz and 192kHz are the sample rates that come along with most high-end recording equipment. Would you believe that a much higher sample rate is starting to be used in the audiophile market? 2.8MHz and even 5.6MHz are being used to record at super high definition. Just to clarify, the ‘M’ stands for Mega and that’s a million times. Often what these few high definition studios will do is record at 2.8MHz and then up-sample the final bounce down to 5.6MHz.
At this super high definition sample rate you’ll notice that you feel like you’re in the room with the artist. The current problem with this sample rate is that there are few DAWs that will accommodate this sample rate and literally no plug-in available on the market. So no auto tune or UAD EQ. Almost all the processing needs to be down externally through outboard gear. This ends up sounding fantastic, but you have to be prepared to let the mistakes or bad notes slip though. It’s kind of like the old days, right?
I recently recorded with Californian record label and studio, Blue Coast Records. Cookie Marenco has been leading the charge with her super high definition recordings. She gets a new act that she releases every week. You can have a listen to my records here. Also, you’ll notice that she gives you the opportunity to purchase the music at various sample rates. The price goes up as the resolution goes up. She has a loyal following of audiophiles that will only buy the music if it is done at extreme sample rates. It’s really very interesting. There is definitely a shift starting to happen against the super low definition world of mp3s and crushed pop masters.
Can you tell the difference?