Sound is a form of energy that travels in longitudinal waves, requiring matter to transmit vibrations between particles. The speed of sound varies according to the medium, being fastest in solids and slowest in gases. Our ears can detect frequencies between 20-20,000 Hz, perceiving variations in pitch from low to high frequencies and loudness from soft to loud amplitudes. Musical instruments produce sound through vibration of different materials, while other technologies like sonar use sound waves for applications such as locating objects underwater.

1. Sound

2. Overview The Facts of Sound Sound Vocabulary The Ear and Sound Musical Instruments and other uses of Sound Other types of waves

3. The Facts Sound … … is a form of energy produced & transmitted by vibrating matter … travels in longitudinal waves … travels faster through solids than liquids or gases

4. Sound waves travel faster through solids because there are more particles close together to transfer the energy. Sound waves and

5. Speed of Sound Medium (Matter) Speed m/sec gas air (0 o C) 331 air (20 o C) 343 water (25 o C) 1493 liquid sea water 1533 iron 5130 copper 3560 solid glass 5640 diamond 12000

6. Vibration Very fast, repeated backward and forward movement of particles of matter For example, the vibration of the tuning fork creates pure sound. The hammer hits the nail and the particles vibrate making noise.

7. Waves transport energy without moving matter Watch the 3 red dots You will see them vibrate , but not move with the wave to the end. All the particles are vibrating but stay fixed

8. Sound Waves Alternating areas of high and low pressure in the air (compressions and rarefactions)

9. Sound Waves ALL sound is carried through matter as sound waves. In a vacuum there are no particles so sound cannot travel. Alternating areas of high and low pressure in the air (compressions and rarefactions)

10. Sound Waves Because sound waves need particles to be transmitted they are mechanical waves ALL sound is carried through matter as sound waves. In a vacuum there are no particles so sound cannot travel. Alternating areas of high and low pressure in the air (compressions and rarefactions)

11. Sound Waves Sound waves move out in ALL directions from a vibrating object. Because sound waves need particles to be transmitted they are mechanical waves ALL sound is carried through matter as sound waves. In a vacuum there are no particles so sound cannot travel. Alternating areas of high and low pressure in the air (compressions and rarefactions)

12. Compression Where particles are pressed together as the sound wave moves through matter.

13. Compression Where particles are pressed together as the sound waves move through matter For example, a wave travels through the springs just like sound waves travel through the air the places where the springs are close together are like compressions in the air. compression

14. Compressions - The close together part of the wave. Rarefactions - The spread-out parts of a wave. Compression Wave = Longitudinal Wave

15. Longitudinal Wave (Compression Wave) Each wave particle vibrates back and forth in the same direction of the wave.

16. Sound waves covered till now: States of matter (solid, liquid, gas) Speed of sound through matter No sound in a vacuum Vibration Compression + Rarefaction Longitudinal waves Remember that ….

17. Waves transfer energy without moving matter. Frequency= waves/time If you watch the 3 red dots you will see them vibrate, but not move with the wave to the end.

18. Wavelength & Frequency Wavelength is the distance between one part of a wave and the same part of the next wave Frequency is the number of waves passing a point in a certain tme Many waves = high frequency Few waves = low frequency

19. Pitch = Frequency How high or low a sound is Pitch depends on the frequency of a sound wave For example, Low pitch Low frequency Longer wavelength High pitch High frequency Shorter wavelength

20. Frequency is measured in Hertz For example: If 20 waves are made per second, then the frequency is 20 cycles per second = 20 Hertz Hz

21. 20 Hz – 20,000 Hz The human ear can only hear sounds between 20Hz and 20,000 Hz (Frequency/Pitch) Below 20 Hz is called infrasound Above 20,000 Hz is called ultrasound

22. Ultrasound sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20,000-100,000Hz Infrasound sounds waves with frequencies below the normal human range of hearing. Sounds in the 0.001 - 20Hz range

23. The Ear Sounds reach our ears through vibrating air particles Our ears capture sound waves and turn them into signals that go to our brains Sound waves move through 3 parts of the ear; outer ear , middle ear , + inner ear

24. The Human Ear

25. Amplitude is the maximum distance the particles in a wave vibrate from their rest positions.

26. Amplitude = loudness The intensity of a sound decreases as you move away from a sound. The sound is softer. As the source of a sound comes closer the sound becomes louder, more intense A loud sound has a high amplitude A soft sound has low amplitude soft loud

27. Amplitude = loudness The volume or loudness of sound is measured in decibels dB

28. Loudness of Sound in Decibels Sound Loudness (dbs) Hearing Damage Average Home 40-50 Loud Music 90-100 After long exposure Rock Concert 115-120 Progressive Jet Engine 120-170 Pain

29. Sound and Instruments Different musical instruments create different sound vibrations Wind instruments by blowing and vibrating the air e.g. flute, saxophone, organ String instruments by touching and vibrating the strings e.g. guitar, violin, piano Percussion instruments by hitting a surface e.g. drums, cymbals, triangle

30. Sound and Instruments Instruments can be played at different pitches (musical notes) by changing the lengths of different parts. For example, Another way to make different pitches is to change the thickness of the material that vibrates. A trombone’s mute absorbs some of the sound waves produced, so a different sound is made.

31. Sonar Sonar uses reflected sound waves (echoes) to find objects in water or air Animals use sonar or echo location to find their prey (food); these sounds have such a high pitch or frequency that the human ear cannot hear them Humans use sonar to locate or find objects

32. Ultrasound (above 20,000 Hz) Ultrasound waves are used in medicine They are also reflected sound waves

33. Other types of waves Remember sound waves are longitudinal and mechanical Other waves are transverse, electromagnetic and water waves

34. Transverse waves wave particles vibrate in an up-and-down motion.

35. Transverse waves Crests - Highest part of a wave Troughs - The low points of the wave

36. Electromagnetic waves Electromagnetic waves travel as transverse waves Electromagnetic waves CAN travel through a vacuum Light, microwaves, x-rays, and TV and radio transmissions are all examples of electromagnetic waves

37. Water Waves The blue surface particles move in a clock-wise direction

38. Wave concepts covered in this power point: Sound Waves States of matter (solid, liquid, gas) Speed of sound through matter No sound in a vacuum Vibration Compression + Rarefaction Longitudinal waves Wavelength Frequency = Pitch Hertz Hz 20 – 20,000 Hz Ear ( outer, middle, inner ear) Amplitude = Loudness = Volume Decibels dB Sonar Ultrasound, infrasound Other waves Transverse waves Crests Troughs Electromagnetic waves Water waves

39. That’s all folks!