Once captured by a microphone (or direct recording device) the musical energy is either recorded on to tape or converted to digital information and stored as a file – either way the physical energy is converted to electrical energy.
A device called an analog-to-digital converter (ADC) takes the electrical energy and converts it to a digital file for storage. The ADC samples the frequency and amplitude at a set rate. Once the music is converted to binary information (1s and 0s) it is stored as a digital file. Music that remains in the analog domain is stored on tape or vinyl.
Take whatever song you’re thinking of right now and freeze it in time – that’s what an ADC does, several tens of thousands of times a second. We may take 44,100, 48,000, 96,000 or 192,000 individual ‘samples’ of each second of a song. The more samples we take, the more information we gather about the sounds of the song, and the more detailed and ‘true’ the song will sound when it is reproduced.
The number of samples we take of each second of music is called the sampling rate. The more frequently you sample, the more information you retain, so it stands to reason that a sample rate of 96 kHz will sound better than a sample rate of 48 kHz but not as good as 192 kHz. Pro audio recording typically samples at a rate of 192 kHz (4 times 48 kHz which is the broadcast standard for video applications).
It’s not just the number of samples we take, but the amount of the sampled information we store that also makes a difference in how a digitized song sounds. This is where bit depth comes in – the deeper the bit depth (larger the data word) the higher the resolution.
Red Book CD uses a bit depth of 16-bits and was the industry standard for many years. As storage capabilities and processing power has increased (and come down in cost) 24-bit resolution has become standard; it won’t be long before 16-bit is no longer supported. Dynamics are particularly affected by bit depth, and by adding those extra 8-bits of data our ability to maintain the dynamics of a musical passage is greatly enhanced. If you listen to music that is not very dynamic you’ll have a hard time hearing the difference between 16- and 24-bit. This is why popular music in the mp3 and lo-res file age (from about 2001 to 2015) purposely de-emphasized dynamics in the production – we couldn’t hear it so why obsess over putting it in there in the first place!
That’s where digital compression comes into play. In order to fit as much music in as small a space as possible we learned how to compress the digital file – basically by removing data that is not absolutely necessary to the coherence of the song. The basic notes and sounds were still there but the life and dynamics were removed. Through ear buds or a tiny little speaker on a portable device you can’t notice the missing information, but when you listen on a system with even slightly more capability you definitely notice the missing bits. The higher in quality your audio system, the more you’ll notice lower quality recordings and storage formats.
This was all because of storage. We increase the resolution of the file from 65,536 possible data values (per sample) to 16,777,216 data values when we jump from 16- to 24-bit, but we also increase the size of the file thirty-two times! This seriously limited the amount of music you could store on a device such as a phone or iPod. Think of it this way: a vinyl LP stores 44 minutes of music (22 minutes per side) and a standard CD stores 80 minutes of music. Thanks to advances in storage technology, today’s mobile devices can store literally thousands of more minutes of music, so it is no longer necessary to rip all of the nuance, dynamics or humanity from a song in order to carry it around with us or stream it. So long mp3!
When you listen back to your digitally stored music, the data passes through a Digital-To-Analog Converter (DAC) where the 1’s and 0’s are converted back to electrical analog energy. A lot of processing goes on in the DAC to smooth out all of those square binary edges, and in fact the signal is never really totally smooth again, but with a high-enough quality DAC you’ll never notice.
All of this has absolutely nothing to do with bit rate, which is the speed with which we digitally transmit information (from your computer through your router to your LSX for example). Bit-rate is the capacity of a digital transmission system to transmit data: The higher the bit-rate the more cohesive and detailed your music or video will be.
So, there’s a really basic primer on how digital audio works. It’s all about numbers: the higher the resolution the more satisfying – magical – your musical experience. You can love your music no matter how you listen, but you can love your music even more when you take advantage of everything today’s awesome technologies have to offer.