Stewarts Production Adventures Yr1

Learning how to be good at production

SND 2: Theory and teenage frequency


A theory lesson

Sound is vibrations in gas, solid and liquid.

sound diagram

The line in the middle is 0/neutral, and the amplitude is the difference between neutral. The bigger the wave, the bigger the sound level/loudness. Also the longer the wave, the lower the pitch.
Notice the wave is identical for both sides.

Sound and the Ear

When you break the sound barrier, it’s called a sonic boom

The time for sound to travel a distance is measured in feet.

  •  From stage to tech desk: about 1/2 second difference
  • Not much of a delay between person and speaker
  • People will hear speaker first, and so people may associate sound with the speaker and not the person
  • Sounds from person and speaker could sound like an echo/smear each other out

Sound Frequency: hurtz

People can hear frequencies from 20 Hz to 20,000 Hz (Measuring from low to high)

1,000 Hz = 1KHz


dB: Decibel

Decibel is a measure of change, not a measure of sound.

SPL: Sound Pressure Level

Sound Pressure level measures amplitude/loudness

Remember that how loud the music is, is called loudness. It’s also called level when you talk about operating machinery. Contrary to popular belief, it’s not called volume because that’s about measuring in 3 dimensions. Even when it says volume, it’s wrong.


Lowest sound pressure level: 0dB (Mosquito flying ¾ from your head)

Highest sound pressure level: 194 dB (The air cannot handle any more than that.)

85 dB: When the sound level is above 85dB for an average of 8 hours, it will damage your hearing. For every 0.3dB added, the time gets halfed. Your employer must give you hearing protection. Even if it makes the sound level quieter by 15 dB, it will help a lot.

8.8dB; 4 hours

9.1dB: 2 hours

9.4dB: 1 hour

9.7 dB: 30 minutes

100dB: 15 minutes, etc.

180 is when your hearing tissue dies.

Threshold of discomfort: 112dB – 120dBsp power of 2

“                                              “ pain: 130 – 135 dBsp power of 2

Remember that audiences have no rights to have hearing protection.

What is a sound system?

  • Changes volume of sounds
  • Input: Microphone
  • Output: Speaker, Transducer (Transducer: converts a signal from one form to another
  • Signal Processing Interconnects
  • Music/Sound Playback
  • Rate Amplify – Pre-amps, Power Amps
  • Slight Delay

Sound System

Remember Loudness=Level, so when someone asks you to change the sound level, you know what to do!

What is a sound operator?

  • Make sure the sound system works
  • Rigging + Sound Setup
  • Line/ Sound Checking
  • Hearing and listening trained
  • Triggering sound cues Stage Action, from sound cues, stage action and calling cues
  • Altering levels of mixing – with Sound Designer’s permission
  • Needs to communicate professionally, remembering to be nice and polite. End things with ‘Please’
  • Works as a team
  • Turns up early
  • Be prepared to learn 🙂


Finally the teen frequency. It’s 17Hz and only young people can hear it. I can hear it! Unfortunately it’s used to scare hoodies out of shops.


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This entry was posted on October 20, 2013 by in Sound and tagged , , .
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