The audio world is awash in terms and numbers, and here are few I think are worth understanding, including 1411 kbps, 20-20,000Hz, multitracking, and stereo.
1411 kbps: Kilobits per second. Hi resolution audio files, the ones you listen to on a CD are produced at 1411 kbps (On a PC, it’s called a WAV file. On a Mac, it’s called an AIFF). As this number drops, the quality of the audio drops, too. Most MP3s are produced at 320 kbps, or perhaps as low as 128 kbps. As the numbers drop, you can hear an odd, swishy, almost watery sort of sound as you listen to the music. Young folks are used to this low level of quality, and probably don’t realize it doesn’t sound that good. Many assume that all digital sounds great. Lower numbers mean some of the audio is being stripped out, so the file size gets smaller, and therefore, you can store more songs on your iPod/smartphone, and it’s easier to stream smaller files across the internet. That’s the advantage. The files are also referred to as lossy, because you are losing audio info and cannot get it back. That’s how the file gets smaller. It’s simple math: 320 of something is a lot less than 1411 of the same!
There is a debate whether you can hear the diff between a 1411 kbps file, versus a lower rez file, like a MP3 made at 320 kbps. I think the difference is small, but can be heard if you have a pretty durn good stereo to compare them on. MP3 technology has actually been around for several decades, even if the public only became aware of it in the last several years. MP4 (or AAC) technology is an improvement upon MP3s. A 320 MP4 should be some level of better than a MP3 at 320. It’s pretty easy to hear the diff if you compare a 1411 to say, a 128. 128 might sound decent for a podcast, but pretty bad for a song. Many other file types exist, like Apple Lossless and FLAC. Both those files are lossless, but the file sizes are larger than MP3s or 4s.
20-20,000 Hz (Hertz): The frequency range of human hearing. Sound is a vibration in an atmosphere, yes? Low frequencies (bass notes) vibrate, or cycle more slowly, the lowest note a person can hear is 20 Hz (or 20 CPS, cycles per second). So that note vibrates/cycles 20 times in ONE second. The highest frequency or treble note is 20,000 Hz, so it vibrates 20,000 times in ONE second. CDs are mastered to make sure that 20-20 KiloHz is available on the CD, but old-fashioned FM radio limits the range, typically to around 30-15,000 Hz. As we age, we can’t hear the lows or highs so well, not to mention if you’ve listened to loud music too much in your life! Named for German physicist Heinrich Hertz (we used to use the term CPS, but no more). Yes, dogs can hear above 20Khz.
Multitracking: Most stereo recordings made after the mid 1960s…like when you listen to a vinyl record, CD, or streamed over the ‘net, have been produced, or mixed down from a multitrack recording. So the guitar is recorded on one track, the vocal on track two, the piano on track three, the bass on track four, etc. The four (or multiple) tracks are mixed down to just two, to create two channel stereo. Tape machines of the past could record 4, 8, 16, even 32 separate tracks on one roll of tape. Digital allows for even more channels.
Multitracking heralded the modern era of recording, as it allows the musicians to record just one part at a time, rather than the whole band playing at once. All recordings made before multitracking were essentially recorded live in the studio, onto one, two, or sometimes three tracks. The band had to play live, and if they made a mistake, the recording was often stopped, and they started all over again until they got it right. Elvis Presley was famous for recording dozens of takes until he felt it was right.
Is one way better than the other? Some would say the old days of bands recording live in studio sounded, well, more like the real band. But multitracking allows for mistakes to be easily fixed or redone. In fact, you can be a one man (or woman!) band, recording all the parts yourself if you want, which was impossible in the past. Some bands record live in the studio, while multitracking. So if there is a mistake, it’s easily fixed, but you get the vibe of the band playing together. Perhaps the best of both worlds.
Stereo #1: Two channels of audio, coupled with multitrack recording, produce what we think of today as stereo playback. Stereo was invented in the late 1950s. Before that, all music was listened to in mono, or one channel, with one speaker. If you listen to mono over two speakers, what comes out of the left is the same as the right, and remains mono. True stereo reproduction means the left channel has some information that is different from what you hear from the right channel. This allows you to sit in front of a pair of speakers (or over headphones) and note that the guitar is coming from the left channel, the singer in the middle, the piano is on the right side, etc. The same song over a mono system would reproduce the guitar, vocals and piano dead center, or in the middle of the two speakers. Stereo is one of the most misunderstood terms we use.
Stereo’s two speakers create a soundstage in front of the listener, as if you were actually in the room with the band (guitar left, vocal middle, piano right). Stereo creates width. It’s a more realistic impression of the music than mono, and is usually a more pleasing listening experience than mono. But I’m not saying all mono is bad, some mono recordings/mixdowns are better than stereo recordings. See #4 below!
Stereo #2: Sometimes we think of “a stereo” as the electronics we listen to, like a stereo receiver or an iPod, and that would be a correct use of the term, too.
Stereo #3: True stereo recording happens when we use two matched microphones in front of, say, a vocalist or acoustic guitar, usually in a X-Y pattern. The two mics (instead of the usual one) don’t just record the person singing, they do a better job of recording the space around them, the “air,” if you will (after all, sound is a vibration in the air). This gives the recording depth, width and life that one mic cannot. Most songs are NOT recorded this way. Photo at left is shot from above the two mics.
Stereo #4: Stereo versus mono mixdowns. The Beatles are probably the best example of how stereo changed the recording industry. They would record a song, and create both a stereo and mono vinyl record for the public to buy. Early in their careers the Beatles were in the control room, assisting with the mixing of the mono version, then sometimes left the stereo version to be mixed by producer George Martin. In other words, there are some differences in the way the stereo version sounds, versus the mono. The stereo version might have the guitar louder than the mono, or the vocals sounded different. The Beatles finally released the Mono Box Set in 2009, rewarding fans who felt the mono recordings were superior and more faithful to the Beatles themselves. But there are plenty of exceptions, where the stereo version is considered better. Just depends on your taste! Stereo was considered a novelty when it was invented. Everyone was used to mono and had to buy new equipment to accommodate the second channel. But if you listen carefully to many new recordings made today, say for a TV commercial, podcast or on radio, you’re often listening to a mono mixdown. Mono still exists, ya just don’t know it!
Decibels (dB): OK, I can’t claim to be able to explain the math behind this, but I can tell you that, say, 6dB is NOT twice as loud as 3dB. Don’t believe me? Read this article by guru Julian Hirsch, of Stereo Review, in 1991.