What do you know about (Frequency) …? [AQ Series: Episode 2]0

To compare the range of frequencies in human experience, a video signal – for example – has an upper frequency of around 5 MHz (depending on the particular system in use in your part of the world). The Olympic Games have a frequency of 8 nanohertz (they happen once every four years!).

• 1 hertz (Hz) means one cycle of vibration per second
• 1000 Hz = 1 kHz
• 1,000,000 Hz = 1 Megahertz (1 MHz)

Sound comes in virtually all frequencies but our hearing system only responds to a narrow range. The upper limit of young human ears is usually taken to be 20 kilohertz (kHz) (twenty thousand vibrations per second). This varies from person to person, and decreases with age, but as a guideline it’s a good compromise. If a sound system can handle frequencies up to 20 kHz then few people will miss anything significant.

At the lower end of the range it is difficult to know where the ear stops working and you start to feel vibration in your body. In sound engineering however we put a figure of 20 Hz on the lower end. We can hear, or feel, frequencies lower than this but they are generally taken to be unimportant.

Frequency is related to wavelength by the formula:

velocity = frequency x wavelength

This applies to any wave motion, not just sound. The velocity, or speed, of sound in air is a little under 340 meters per second (m/s). This varies with temperature, humidity and altitude, but 340 m/s is a nice round number and we’ll stick with it. If you work out the math, this means that a 20 Hz sound wave traveling in air has a wavelength of 17 metres!

The extreme physical size of low frequency sound waves leads to tremendous problems in soundproofing and acoustic treatment. At the other end of the scale, a 20 kHz sound wave traveling in air has a wavelength of a mere 17 mm. Curiously, the higher the frequency the more difficult it is to handle as an electronic, magnetic or other form of signal, but it is really easy to control as a real-life sound wave traveling in air. Low frequencies are easily dealt with electronically, but are very hard to control acoustically.

Producer / Composer
Ahmed Al-Qarawi
SOUND VISIONS

E: soundvision7@yahoo.com
E: tune.trade@yahoo.com
http://www.soundvisions.ws

http://www.tunetrade.net

Attention: This article is copyrighted to Ahmed Al-Qarawi, please collect his approval before referring to it.

About Ahmed Al-Qarawi

I’m Music Producer / composer & Owner of sound vision Production company in Kuwait for over 15 years now, I have been scoring music for Serials /Commercials / short film and Musical Albums for over 10 years.I would be delighted to discuss any future opportunities.

Top ear image credit: Camera press / Madame Figaro / Phi

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