Intermediate 1 Sound and Music Revision

1. Intermediate 1Sound and Music Revision

2. Sound and Music • In this topic there are 2 equations: • Speed = distance/time • Voltage gain = Voltage out/voltage in

3. http://egfl.net/Teaching/Resources/Animations/homepage.html • Sound is caused by vibrations. • Sound travels in solids, liquids and gases, but cannot travel in a vacuum. • Sound travels fastest through a solid, next fastest through a liquid, and slowest in a gas. • The speed of sound in air is 330m/s

4. Sound Waves If an object is to produce sound, it must vibrate. The sound produced travels as a wave which transfers energy from one place to another.

5. Sound Waves Frequency is the number of waves passing a point in one second. Frequency is measured in Hertz (Hz). wavelength

6. If an object produces 56 sound waves every second it has a frequency of 56 hertz.

7. Loud and Quiet Sounds Quiet sound Loud sound

8. What happens when you change the frequency? You get more waves in the same time.

9. If you increase the frequency of a musical note, you are increasing the number of waves produced every second and you increase the pitch of the note. This oscilloscope shows traces taken for two sounds. They both have the same loudness (or volume). The red trace is a sound of higher pitch because it has more waves and so a higher frequency.

10. If you increase the amplitude of a musical note, you are increasing the energy of the wave and you increase the volume of the note. This oscilloscope also shows traces taken for two sounds. They both have the same frequency (or pitch). The red trace is a louder sound because it has a higher amplitude (and more energy) so a louder volume is produced.

11. Sounds can be compared in octaves. Two notes may be given the same letter but they are different notes. The notes with the same letter will be one or more octaves apart, “middle” E is one octave above “low” E. When two sounds are one octave apart, the frequency of one is double the frequency of the other.This means that “middle” E has double the frequency of “low” E.

12. The higher the frequency, the higher the pitch. We will look at some musical instruments… What causes the sound of a guitar playing? Vibration in the string.

13. The higher the frequency, the higher the pitch. We will look at some musical instruments… B A If you put your finger on the points shown, which position would give you the highest pitched note? A or B? B, because the shorter the string, the higher the pitch (frequency).

14. The higher the frequency, the higher the pitch. We will look at some musical instruments… B A If note A has a frequency of 100Hz, would the frequency of note B be more or less than A? The frequency of note B would be more than note A, because the length of string is shorter. Suggestion….?

15. The higher the frequency, the higher the pitch. What causes the sound of a recorder playing? Vibration in column of air.

16. The higher the frequency, the higher the pitch. What causes the sound of a recorder playing? Vibration in column of air. When you put your fingers over the holes in the recorder, how is the note changed? You are changing the length of the column of air. The shorter the length of the column of air, the higher the frequency.

17. Why do we see lightning and hear the thunder a few seconds later? The speed of light is much faster than the speed of sound.

18. Speed of Sound How did we measure the speed of sound ? We measured the length of the playing field by measuring one stride with the metre stick and counting the number of strides. We measured the time difference between seeing the cymbals clashing before hearing the bang with the stopwatch. We used the equation speed = distance/time to calculate the speed of sound.

19. Speed of Sound How did we measure the speed of sound more accurately? We measured the distance between the microphones. We made a sound by clapping our hands. We used a computer to calculate the time between each microphone picking up the sound. We used the equation v = d/t

20. Fast timer Clap hands here 1 metre

21. Range of Human Hearing • The range of human hearing is 20Hz to 20,000Hz Above 20,000Hz: Ultrasound

22. You can use ultrasound to view the unborn baby in the mother’s womb.

23. You can use ultrasound to find out the depth of the sea bed, using echo-sounding. http://www.punaridge.org/doc/factoids/Sound/

24. Suppose this ship sent out a sound wave and got an echo back after 4 seconds. How long did it take for the sound to get to the sea bed? If the depth of the sea is 3000metres, what is the speed of sound in water? Speed = distance/time = 3000/2 = 1500 metres per second.

26. Suppose this ship sent out a sound wave and got an echo back from a fish after 0.6 seconds. How long did it take for the sound to get to the fish? If the depth of the fish is 450metres, what is the speed of sound in water? Speed = distance/time = 450/0.3 = 1500 metres per second.

27. If the fish is nearer the surface of the water, what happens to the time taken to receive the echo? Shorter time, because shorter distance to travel

28. If the fish is nearer the seabed, what happens to the time taken to receive the echo? Longer time, because longer distance to travel

29. Some examples of typical sound levels are: Threshold of hearing 0 dB Whisper 20 dB Background noise at home 40 dB Ordinary conversation 60 dB Loud conversation 70 dB Door slamming 80 dB Heavy lorry passing 1m away 90 dB Pneumatic drill 100 dB Rock group loudspeaker at 1m 110 dB Threshold of pain 140 dB Any sound of 90 dB or above is considered to be noise pollution, and can damage hearing.

30. Noise Noise is measured in decibels (dB) Frequency is measured in Hertz (Hz)

31. Noise How can you protect your ears from loud noises? Wear ear protectors

32. Noise How can you protect your ears from loud noises? Turn down the volume

33. Amplified Sound In order to amplify a sound signal, there are three main parts to the required system. 1. The microphone. The purpose of a microphone is to change the sound energy into electrical energy. The amplifier takes the electrical energy and increases the strength of the signal. 2. The amplifier. 3. The loudspeaker. The loudspeaker takes the stronger electrical signal and turns it back into sound energy, which is now much louder.

34. A Public Address System: (Tannoy) How do you calculate voltage gain? 40V 0.2V amplifier Voltage Gain = Voltage Out Voltage In Voltage Gain = 40/0.2 = 200

35. A Public Address System: (Tannoy) When the signal is amplified, what happens to the frequency? 40V 0.2V amplifier Nothing!

36. When people hear their own voice on a recording they do not always believe that they really sound as they do on the recording. This is because we normally hear our own voice due to vibrations of the bones in our ears and our skull and vibrations in the air as detected by our ears. When we listen to a recording of our voice we hear it by the vibrations in the air as detected by our ears only.

37. Compact discs (CDs) have various advantages over a normal tape cassette. These advantages include that there is no wear and tear of the disc when it is played. A CD will produce very little background noise when compared to a normal cassette tape playing. You can go straight to the part of the recording that you want to hear instead of having to ‘fast forward’.