8.3 Sound: levels

• Science
• Middelbare school
• vwo
• Leerjaar 1

Learning goals

5.3 Loudness and the decidbel scale

• • Name the unit of sound intensity.
  
• • Explain which two factors influence the amount of decibel measured.
  
• • Explain how the deicbel scale works and be able to do simple calcualtions with it.
  
• • Name three ways of reducing the risk of loud noises.  

Four wave properties

1. Amplitude

2. Frequency 

3. Speed

Amplitude: how hard or intensive a sound is

3) Which of these two waves has a higher amplitude? Explain.

Image 1

Image 2

4) Listen to these two sounds. Of which does the sound wave have a higher amplitude?

Sound A

Sound B

• Make sure to be in presentation mode.
• Click the icon to play the sound.
  
• Make sure to keep the volume of your computer the same!

4) Listen to these two sounds. Of which does the sound wave have a higher amplitude?

Sound A

Sound B

• Make sure to be in presentation mode.
• Click the icon to play the sound.
  
• Make sure to keep the volume of your computer the same!

The soundwaves of sound B have a higher amplitude, because the sound is louder.

Recap

What did we cover previous lesson?

Outer ear

• Collect sounds waves, channels them to the middle ear
  

Middle ear

•  Amplifies the sound waves

Inner ear

• Turns the wave pattern into an electric signal so that it can be send to the brain through nerves

Four types of hearing loss

•  A hole in your ear drum — this heals over time

•  Getting wax build up in your ear — this can be removed

• An ear infection, fluid builds up in your middle and inner ear.

• Your auditory nerve or system can get damaged or be fautly

A simulation

Link

The decibel-scale

The decibel (abbreviated dB) is the unit used to measure the intensity (loudness) of a sound.

• The unit of Loudness: decibel (dB)
• If you double the number of the sound source, the loudness increases by 3 decibles 

• you measure the sound intensity with a decibel meter

If you double the number of the sound source, the loudness increases by 3 decibles 

For every 10-decibel increase in the intensity of sound, loudness is 10 times greater. 

For example:

• A 40 db sounds is 10 times louder as 30 db sound.
  
• A 50 db sounds is 100 times louder as a 30 db sound (10 x 10)
• A 60 db sound is 1000 times louder as a 30 db sound (10 x 10 x 10)

dB(A)

You will often see noise levels given in dBA instead of dB. Measurements in dBA, or dB(A) are decibel scale readings that have been adjusted in to the varying sensitivity of the human ear. 

Threshhold of hearing

Is when you start hearing the sound. 

Threshhold hearing for adults is 0 dB ( very soft sound)

3 ways of reducing risk of  loud noises

1.shielding. using ear defender such as earplug

2. Moving away from the sound source

3.reducing the time that you listen to loud noise

Assignment 

In a football stadium the loudness is measured at the centre of the pitch. If 1000 people cheer the loudness is 80 dB. What will the loudness be if 100.000 people cheer?

– 1000 mensen: 80 dB

– 2000 mensen: 80 + 3 = 83 dB;

– 4000 mensen: 83 + 3 = 86 dB;

– 8000 mensen: 86 + 3 = 89 dB;

– 16 000 mensen: 89 + 3 = 92 dB;

– 32 000 mensen: 92 + 3 = 95 dB;

– 64 000 mensen: 95 + 3 = 98 dB;

– 128 000 mensen: 98 + 3 = 101 dB.

Loudness(sound intensity) of 100 000 is about 100 dB