Sound What is ultrasound? What do we use it for?

How do you become deaf? You can damage your hearing when you hear a very loud noise e.g. over 130dB. This can make a hole in your ear drum. You can also damage your hearing by listening to loud noises eg. about 85 dB to 120 dB for a long time. How loud do you think these sounds are: Whisper Normal conversation Noisy classroom Motorcycle Car horn Headphones siren

How do you become deaf? You can become temporarily deaf by listening to a loud noise e.g. about 80 to 100 dB for a short time ( a few hours) You can become permanently deaf when you hear a very loud noise e.g. over 130dB. This can make a hole in your ear drum. You can also become deaf by listening to loud noises eg. about 80 to 100 for a long time. How loud do you think these sounds are:

How can you protect your ears? Use ear plugs – protective headphones. Don‘t listen to loud noises for a long time. Read the worksheet – answer the questions and highlight important facts.

What frequency can you hear? Listen – put your hand up when you can hear something.

Ultrasound What is ultrasound? Any sound which is too high for humans to hear – usually over 20,000Hz or 20kHz. How do we use ultrasound? We use ultrasound to examine things we can‘t see. A sound generator sends sound waves at an object and measures the time it takes to come back - the shorter the time, the nearer the object is. Why is it useful? Because we can look at things without cutting them open for example.

Now do - the worksheet on the ear - and then recap on sound quiz.

Check your answers. 2.Which part of the ear changes the sound waves into an electrical signal? 3.Which part of the ear passes the vibrations from the eardrum to the cochlea? 4.What are the three semi-circular canals for? 5.What is a noise? 6.What is volume measured in? 7.How can you become temporarily deaf? 8.How can you become permanently deaf? 2. The hairs in the cochlea - cilia 3. The ossicles 6. Decibels 4. Balance 5. An unpleasant sound 7. Listening to too loud noises (> 80 dB) for some time. 8. Listening to too loud noises (> 80 dB) for a long time or a very loud noise (>120dB) for a short time.

Step 5: Answers. 9.Why do you become deaf? Describe what happens to the ear? 10.Put these noises on the scale below: normal conversation, jet plane, thunder, lorry, bird’s singing, motorbike, 11.What volume can cause somebody to become deaf? 12.How can you protect your hearing? 13.What is the hearing range of a human? 14.What frequency is ultrasound do you think? to 20,000 Hz 9. The hairs in the cochlea are damaged or the ear drum can be perforated (has holes in). 11. Above 120 dB ?? 10. Jet plane – 130dB; thunder – 115 dB; lorry – 100dB; motorbike – 85dB ; normal conversation – 45dB; bird‘s singing – 25dB 12. Above 120 dB

Sound!. Think about these questions: What gives the highest note? A big or a small tuning fork? And why? What happens to the amplitude and pitch of a wave when you move away from it? If two people play clarinets 100 metres away, which will you hear first, the higher or the lower note? Why does a noise in an empty room seem quieter than a noise in a room with lots of people?