Sound (11-16) Click here to buy the clear version of Sound (11-16). This pdf file can be downloaded and used on your PC or tablet.

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1 Sound (11-16) Click here to buy clear version of Sound (11-16). This pdf file can be downloaded and used on your PC or tablet. NOT AVAILABLE YET TEST PAGES ONLY

2 Contents Topic Page Contents Page Sound waves 3 Faster than sound 15 Notes and noise 4 Sound in tubes 16 Quality of notes 5 Ultrasonics 17 Sound in different materials 6 18 Musical notes 7 19 Organ pipes 8 20 The ear (1) 9 21 The ear (2) The speed of sound The loudness of sounds Reflection of sound Refraction of sounds 14 26

3 Sound waves Sound Click waves travel through air by air box molecules vibrating backwards and forwards. This backwards and forwards motion of molecules in a sound wave means that sound waves are LONGITUDINAL WAVES. The faster vibration higher pitch of note and bigger vibration louder note. title page to buy Sound waves can t travel through vacuum. It needs a material transmit vibrations On Moon where re is almost no air sound would not travel from one place to anor. You could see an explosion but not hear it. clear version

4 Notes and noise Click box on Some sounds are pleasant and some rar unpleasant. That is difference between noise and music. You can see shape of sound wave by looking at trace that it makes on an oscilloscope screen. title page to buy On oscilloscope a noise will look like a ragged jumble of ups and downs, usually A pure note noise with sharp peaks and troughs. A pure clear note will be a smooth version wave with no quick changes. A loud, high pitched note The size and shape of wave produced by a pure note will depend on Cost pitch 1 of note and how loud it is. A loud, low pitched note A soft, high pitched note A soft, low pitched note

5 Quality of notes Click box on smooth A note sung by a man will sound different from same note sung by a woman, and if played on different instruments it will also sound different each time. title page to buy These slightly different sounds all have harsh same pitch or frequency it s just shape of wave that is different. The more jagged wave harsher sound. clear version very harsh It is combination of different types of sound that gives different sorts of music its own characteristic sound!

6 Sound in different materials Click box on Sound waves travel at different speeds in different materials: vacuum Material title Speed of page sound (m/s) to buy bell Air (at 293 K) 320 Water 1500 Steel 6000 bell jar The more tightly molecules of material are held toger clear faster sound will travel. version air pumped out If re are no molecules for sound wave to vibrate it cannot travel and so: Sound waves can t travel through a vacuum

7 Musical scales Click box on There are actually two different musical scales: (a) scientific scale based on middle C having a frequency of 256 Hz, also known as diatonic scale, and (b) musicians scale based on A having a frequency of exactly 440 Hz, also title page to buy known as equally tempered scale. On this scale middle C has a frequency of Hz. (shown below) The frequency ratio for two notes one octave apart is 2:1 while for a fifth it is 1.5:1. On equally tempered scale frequency ratio for each semitone is :1. The ratio for tone interval is sixth root of 2 and that for semitone twelfth root of 2. clear version

8 Organ pipes Click box on An organ pipe in a cold church will be shorter than normal but air molecules in it will be moving slowly and so pitch of note that comes from it will be lower than it should be note will be flat. title page to buy clear version

9 The ear (1) Click box on title page to buy clear version

10 The ear (2) Middle ear bones Click box on The sound is "received" by your outer ear and n travels along outer ear canal until it reaches eardrum. The eardrum is a thin membrane like skin of a drum. This vibrates when sound waves hit it. Pressing on or side of eardrum are middle title page to buy Stirrup bone ear bones. These bones act like a series of levers, magnifying movement produced by eardrum until Eardrum final bone, stirrup bone, starts vibrating. The stirrup bone transmits vibrations to inner ear a hollow organ filled with liquid and with inside cochlea covered in fine hairs. The hairs are sensitive to movement and convert it to a series of electrical impulses. These signals are n carried by nerve to brain you can hear sound. clear version semicircular canals The inner ear is also important Cost in giving you a sense 1 of balance. The movement of fluid in three semicircular canals tells you wher your head is upright or not and if not what position it is in.

11 The speed of sound in air Click box on The speed of sound in air is about 320 m/s. The reason for difference in speed of sound in title page to buy different materials is that sound waves are carried by molecules banging into each or and in air molecules are far apart and not held toger firmly. In steel molecules are held toger tightly and so vibrations pass through steel much faster. Two things affect speed of sound in air (i) wind - if wind is blowing in same direction that sound is travelling n speed of sound is increased. (ii) temperature - colder air slower sound travels. clear version

12 The loudness of sounds Decibel level Typical sound source Click box on Danger of skin burning 140 Jet taking off. Permanent hearing damage possible. 130 Jet engine at 30m. Air raid siren. title Very loud rock page group! Pain. to buy 120 Pneumatic road drill. Jet engine at 150m Damage to hair cells in inner ear. 110 Car horn at 6m. Pop group at 2m 100 Heavy road traffic. 90 Very loud orchestra. Heavy truck (MOT test 92 decibels at 8m). Underground train 80 Alarm clock. Loud hi-fi. clear 70 Busy street traffic. version Vacuum cleaner. Building noise. 60 Normal conversation at 1m. 50 Quiet street. 40 Quiet radio in a house. 30 Rustle Cost of paper. Tick of watch 1 when held to your ear. 20 Whisper. Quiet country lane. 10 Rustle of leaves in a light breeze. 0 Threshold of hearing.

13 Reflection of sound Click box on Sound obeys same laws of reflection but amount of sound and light reflected from different materials is different. The walls of rooms used to test sounds are often covered with soft material or even projections like egg boxes to reduce sound reflection. title The reflection of page a sound is an echo. to buy In concert halls is important to have enough sound reflection but not to much. Too little and building is described as "dead" or "dry", too much and echoes from walls interfere with original music. The more people in a room "deader" it will be as regards sound because clod human body does not board clear version reflect sound very well. cardboard tubes watch or buzzer ear here

14 Refraction of sound Click box on On a hot day air near ground is hot so sound wave bends upwards from hot air into title cold air (Figure page 1). to buy On a cold night air near ground is cold and so sound wave bends downwards. clear (Figure 2) This is why you version can sometimes hear sounds from a long way away if night air is cold.

15 Faster than sound Click box on title page to buy The blue cone shows front of sound wave. The observer does not hear sound until part of that blue cone reaches m. By that time plane will have already travelled past m. This distance gets bigger as plane flies clear faster. version

16 Sound in tubes Click box on The diagrams show how a sound wave "fits in" to size of tube that makes it. They also show title vibrations page of to buy molecules of gas in tube. The note that a tube emits depends on three things: (a) length of tube (b) gas in tube (c) temperature of gas in tube clear version The longer tube is lower pitch of note that it can emit. When a tube is heated it expands and so is longer!

17 Ultrasonics Click box on Ultrasonic is word used to describe range of sound beyond limit of human hearing. Ultrasound has a frequency of at least 30 khz. Uses and effects title of ultrasonics: page to buy 1. Pregnancy scan. Ultrasonic scans are used to look at unborn babies because sound waves are safer than X rays 2. Sonar depth measurement at sea. The speed of sound in water is greater than that in air because molecules of water are closer toger. 3. Producing fine sprays 4. Physiorapy high frequency sound heats up damaged tissue clear and so aids healing version 5. Cleaning dust is literally shaken off by vibrations 6. Ultrasonic welding welding without heat pollution 7. Mixing emulsion paints 8. Burglar alarms involving Cost a Doppler motion sensor 1

18 Sound questions 1. A Click large tuning fork will make a box note than on a small tuning fork. 2. Frequency title is... page to buy that an object makes every.. 3. A note with a low pitch has a.. frequency. 4. A large organ pipe is likely to make a note than one of clear same length but thinner. version 5. An acoustic guitar uses body of guitar to make sound. 6. Sound travel though a vacuum