Frequency is a component of sound, and sound engineers, acoustic engineers, physicists, medical technicians, and rocket scientists all have an interest in frequency: when it comes to sound – frequency matters.
Reproducing sound and projecting it through a speaker means you need a firm grasp of how frequency works in human hearing.
When you hit a drum or strum a guitar, you produce sound because of the vibration of the drum skin or the guitar sting. The vibration is a component of the sound wave. Even without an in-depth scientific study of sound, you instinctively know that sound is all about vibration (remember the song by The Beach Boys – Good Vibrations?). Frequency is the measure of the vibration of sound.
You mainly hear through sound vibrations on your eardrum, but you don’t hear exclusively through your ears. Sound is a vibration, and you can listen to it through your skull and feel it with your whole body – you really can feel the noise.
There are deaf musicians (as opposed to older band members who have hearing loss) like Mandy Harvey, a jazz singer with perfect pitch, and Sean Forbes, Founder of the Deaf Performing Arts Network. Closer to home in Scotland, there is Dame Evelyn Glennie, an award-winning percussionist. All of these musicians demonstrate that you feel and understand sound, as well as hearing it through your ears.
The limits of the best human frequency range are 20 to 20,000Hz. Most people’s hearing is nowhere near that sensitive. The human speaking voice range lies between 1000 and 5,000Hz, and it’s not surprising that most people are best at picking up noises in that range.
Without getting too technical, the human frequency range or audio spectrum divides into:
- Sub-bass: 20 to 60Hz and you feel it more than hear it.
- Bass: 60 to 250Hz. Most music uses bass notes around 90 to 200Hz.
- Low midrange: 250 to 500Hz, sometimes called the bass presence range.
- Midrange: 500 to 2,000Hz, too much in this area can be tinny and tiring on the ears.
- Upper midrange: 2,000 to 4,000 Hz, in the human voice range.
- Presence: 4,000 to 6,000 Hz. In a home stereo, this is the treble area.
- Brilliance: 6,000 to 20,000Hz in this range, you get a bit of sparkle but may also get too much hiss.
Speakers and Frequency
What does all this have to do with speaker design? The speaker produces sound in the human range because let’s face it, that’s what you want. Unless you have some weird reason for playing music to a different species.
The frequency response of your speaker tells you the range of sound frequencies that the speaker can project. It won’t be the full human range, but a section of it. A speaker attempting to project sounds covering the whole human range would sound terrible – you are better off with speakers that project a defined range accurately and without excess colour.
The holy grail of speakers is to take the sound input and project it through the speaker with minimal variation – a flat frequency response. When you are looking at speakers, you need to pay attention to the range and the response. When it comes to designing your sound system, you will blend your use of speakers to cover the range and quality of sound you want the audience to hear. When it comes to speakers – frequency matters.