SOUND Nature and Properties

MAIN IDEA Sound waves are longitudinal waves that travel only through matter.

SOUND air molecules

SOUND SPEED The speed of a sound wave through a medium depends on that medium’s composition & whether that medium is solid, liquid, or gas. MediumSpeed of Sound (m/s) Air (0°C)330 Air (20°C)340 Cork500 Water (0°C)1,400 Water (20°C)1,500 Copper3,600 Bone4,000 Steel5,800

SOUND SPEED Sound travels faster in solids & slower in gases. Why? The particles that make up solids are closer together than the particles in gases

THE EAR Outer Ear Visible part of your ear Ear canal Eardrum – a tough membrane about 0.1mm thick that transmits sound from the outer ear to the middle ear. Middle Ear hammer anvil stirrup Inner Ear Cochlea – a spiral shaped structure that is filled with liquid & contains tiny hair cells

MINI LAB Step 1: Hold a wood block next to your ear. Step 2: Have a partner hold a ringing phone next to the wood block. Step 3: Hold an empty water bottle next to your ear. Step 4: Have a partner hold a ringing phone next to the water bottle. Step 5: Repeat steps 3 & 4 with the water bottle filled with water. Compare and contrast the sound of the phone when it traveled through the three different mediums – this will be a lab grade.

INTENSITY Intensity is the amount of energy that passes through a certain area in a specific amount of time Loudness (and amplitude) depend on the intensity The higher the intensity, the higher the energy needed to create the sound wave Low amplitude High amplitude

LOUDNESS Loudness is the human perception of sound volume and primarily depends on sound intensity The higher the intensity, the more your eardrum vibrates, the louder the sound that you hear A decibel (dB) is a unit of sound intensity

Sustained sounds above about 90 dB can cause permanent hearing loss

PITCH Pitch is how high or low a sound seems to be The higher the pitch the higher the frequency 262 Hz 294 Hz 330 Hz 349 Hz 392 Hz 440 Hz494 Hz 523 Hz

DOPPLER EFFECT The Doppler effect is the change in wave frequency due to a wave source moving relative to an observer moving relative to a wave source

MUSIC Every material has a natural frequency – musical instruments use object’s natural frequencies to create music. The pitch you hear depends on the object’s (ex. string) natural frequency The sound produced by musical instruments is amplified by resonance In a brass or wind instrument the vibrations of a person’s lips or the reed cause the air inside the instrument to absorb energy and vibrate at its natural frequencies

ECHOLOCATION

QUESTIONS 1.How does sound travel through different mediums? 2.What effects the speed of sound? 3.Some people hear ringing in their ears, called tinnitus, even in the absence of sound. Form a hypothesis to explain why this occurs. 4.How are amplitude, intensity, & loudness related? 5.What is the relationship between frequency & pitch? 6.What is the Doppler effect?