Conceptual Physics Notes on Chapter 26 Sound For

Conceptual Physics Notes on Chapter 26 Sound

For Sound To Be Heard… Ø You need 3 things: l l l 1. a source that produces the sound 2. a medium to transmit the sound 3. an organ of the body that detects the sound Ø Sound enters the outer ear, vibrates eardrum, enters middle ear and vibrates liquid-filled inner ear.

For Sound To Be Heard…

Outer Ear The outer ear acts as funnel for the waves. The waves travel through the ear canal and hit the lightly stretched membrane called the eardrum causing it to vibrate. The vibrations then enter the middle ear.

Middle Ear The middle ear contains the 3 smallest bones in the body. hammer, anvil, stirrup The vibrations travel through the 3 bones and are transmitted to a liquid-filled inner ear.

Inner Ear The inner ear contains the cochlea. Cochlea is snail shaped Contains liquid and hundreds of cell attached to nerve fibers The nerve fibers form one larger nerve that travels to the brain where they are interpreted as sound

26. 1 Origin of Sound Ø All sounds are produced by the vibrations of material objects. Sound moves through a medium in the form of a longitudinal wave. Ø Frequency of the sound waves produced equals the frequency of the vibrating source. Ø Pitch describes our impressions about frequency or sound when produced by vibrations. l l High- pitched sounds have a high frequency Low-pitched sounds have a low frequency

26. 1 Origin of Sound ØA “normal” person can distinguish sound frequencies between 20 and 20, 000 hertz. • below 20 hertz is known as infrasonic. • above 20, 000 hertz is known as ultrasonic. NOTE: No human can hear above or below 20 - 20000 hertz.

26. 2 Sound in Air Ø When something vibrates, it causes a wave that compresses and stretches. Ø In physics we call this Compression and Rarefaction. Ø For all wave motion, its not the medium that travels, but a pulse that travels.

26. 3 Media that Transmit Sound Ø Sound needs a medium to travel through. But sound travels at different speeds in different mediums. l Air --- can range from 330 m/s - 350 m/s • NOTE: For ALL problems we will take the average speed of 340 m/s l Liquid - can range from 1325 m/s - 1375 m/s • NOTE: For water we will take the average speed of 1360 m/s (Water) l Solid - Can range from 4500 m/s - 6000 m/s • NOTE: For solids we will take the average speed of 5100 m/s (Steel)

26. 4 Speed of Sound Speed of sound in a gas depends on the temperature of the gas, and the mass of the particles in the gas. l Hear thunder after you see lightening Ø At 0⁰ C in dry air, sound travels 330 m/s or 1200 km/h l each degree above 0, the speed of sound increases by 0. 60 m/s Ø Speed of sound in a solid depends on the materials elasticity (materials ability to change shape in response to an applied force, then resume its initial shape) l Steel is very elastic l Putty is inelastic Ø

26. 5 Loudness Ø Loudness is subjective. Each person hears sound different due to each persons brain interrupts sound different. Loudness is measured in Decibel (d. B). Decibels are based on a logarithmic variation. Ø EX: 40 d. B is 100 times as loud as 20 d. B Ø 100 d. B is 10 times as loud as 90 d. B Ø Physiological hearing damage begins at exposure to 85 d. B.

26. 6 Natural Frequency Ø When any object composed of an elastic materials is disturbed, it vibrates at its own special set of frequencies- forms a special sound Ø Natural Frequency is the frequency at which the object vibrates when it is disturbed. l l Depends on the elasticity and shape of the object. Minimum energy is required to produced forced vibrations

26. 7 Forced Vibration Ø Forced vibration is when a vibrating object causes a object in contact with it to also vibrate.

26. 7 Forced Vibration Ø Sound boards are an important part of all stringed musical instruments because they are forced into vibration and produce the sound. Ø Without the sounding board, the sound would be barely audible.

26. 8 Resonance Ø Resonance occurs when the frequency of a vibration forced on an object matches the object’s natural frequency, causing a dramatic increase in amplitude. Ø An object resonates when there is a force to pull it back to its starting position and enough energy to keep it vibrating.

26. 9 Interference Ø Interference of sound waves affects the loudness of sounds.

26. 9 Interference When constructive interference occurs with sound waves, the listener hears a louder sound. – Increase in Amplitudes Ø When destructive interference occurs, the listener hears a fainter sound or no sound at all. – Decrease in Amplitudes Ø l Ø Antinoise technology uses destructive interference The crest of a transverse wave corresponds to the compression of a sound wave- the trough corresponds to the rarefaction.

Sound Ø Different objects create different sound waves.

Sound Ø Sound waves can produce HARMONICS.

Sound ØHarmonics can be easily demonstrated with a tuning fork and tube.

26. 10 Beats happen when two waves interfere with each other in a way that some of the wave energy overlaps constructively and some overlap destructively. Ø DEF- Periodic variation in the loudness of a sound Ø

Sound l If you subtract the frequencies of the two tuning forks, you can get the beat frequency. • EX: 262 Hz and 266 Hz 262 Hz and 272 Hz

Conceptual Physics Notes on Chapter 26 Sound

For Sound To Be Heard… Ø You need 3 things: l l l 1. a _____ that produces the sound 2. a _____ to transmit the sound 3. an ____ of the body that detects the sound Ø Sound enters the outer ear, ______ eardrum, enters middle ear and vibrates liquid-filled inner ear.

For Sound To Be Heard…

Outer Ear The outer ear acts as _______ for the waves. The waves travel through the ear canal and hit the lightly stretched membrane called __________ causing it to vibrate. The vibrations then enter the _______ ___.

Middle Ear The middle ear contains the 3 smallest bones in the body. _______, __________ The vibrations travel through the 3 bones and are transmitted to a liquid-filled inner ear.

Inner Ear The inner ear contains the ______. Cochlea is snail shaped Contains liquid and hundreds of cell attached to _________ The nerve fibers form one larger nerve that travels to the brain where they are interpreted as sound

26. 1 Origin of Sound Ø All sounds are produced by the vibrations of material objects. Sound moves through a medium in the form of a ________. Ø Frequency of the sound waves produced equals the frequency of the vibrating source. Ø _____ describes our impressions about frequency or sound when produced by vibrations. l l High- pitched sounds have a _____________ Low-pitched sounds have a _____________

26. 1 Origin of Sound ØA “normal” person can distinguish sound frequencies between 20 and 20, 000 hertz. • below 20 hertz is known as _______ • above 20, 000 hertz is known as ______ NOTE: No human can hear above or below 20 - 20000 hertz.

26. 2 Sound in Air Ø When something vibrates, it causes a wave that ______ and _____. Ø In physics we call this Compression and Rarefaction. Ø For all wave motion, its not the medium that travels, but a ____ that travels.

26. 3 Media that Transmit Sound Ø Sound needs a medium to travel through. But sound travels at different speeds in different mediums. l Air --- can range from _____ - _____ • NOTE: For ALL problems we will take the average speed of 340 m/s l Liquid - can range from _______ - _____ • NOTE: For water we will take the average speed of 1360 m/s (Water) l Solid - Can range from ____ - _____ • NOTE: For solids we will take the average speed of 5100 m/s (Steel)

26. 4 Speed of Sound Speed of sound in a gas depends on _______ of the gas, and ____________ in the gas. l Hear thunder after you see lightening Ø At 0⁰ C in dry air, sound travels 330 m/s or 1200 km/h l Each degree above 0, the speed of sound increases by 0. 60 m/s Ø Speed of sound in a solid depends on the materials _______ (materials ability to change shape in response to an applied force, then resume its initial shape) l Steel ________ l Putty ________ Ø

26. 5 Loudness Ø Loudness is _______. Each person hears sound different due to each persons brain interrupts sound different. Loudness is measured in _________. Decibels are based on a logarithmic variation. Ø EX: 40 d. B is 100 times as loud as 20 d. B Ø 100 d. B is 10 times as loud as 90 d. B Ø Physiological hearing damage begins at exposure to ______d. B.

26. 6 Natural Frequency Ø When any object composed of an elastic materials is disturbed, it vibrates at its own special set of frequencies- forms a special sound Ø _________ is the frequency at which the object vibrates when it is disturbed. l l Depends on the _______ and ____ of the object. Minimum energy is required to produced forced vibrations

26. 7 Forced Vibration Ø __________ is when a vibrating object causes a object in contact with it to also vibrate.

26. 7 Forced Vibration Ø __________ are an important part of all stringed musical instruments because they are forced into vibration and produce the sound. Ø Without the sounding board, the sound would be ____________.

26. 8 Resonance Ø Resonance occurs when the frequency of a vibration forced on an object matches _____________, causing a dramatic increase in amplitude. Ø An object resonates when there is a force to pull it back to its starting position and enough energy to keep it vibrating.

26. 9 Interference Ø Interference of sound waves affects the loudness of sounds.

26. 9 Interference Ø When ________ interference occurs with sound waves, the listener hears a louder sound. – Increase in Amplitudes Ø When _______ interference occurs, the listener hears a fainter sound or no sound at all. – Decrease in Amplitudes l Antinoise technology uses destructive interference Ø The _______ of a transverse wave corresponds to the ________ of a sound wave- the _____ corresponds to the ________.

Sound Ø Different objects create different sound waves.

Sound Ø Sound waves can produce _______.

Sound ØHarmonics can be easily demonstrated with a tuning fork and tube.

26. 10 Beats happen when two waves interfere with each other in a way that some of the wave energy overlaps constructively and some overlap destructively. Ø DEF- Periodic variation in the loudness of a sound Ø

Sound l If you subtract the frequencies of the two tuning forks, you can get the beat frequency. • EX: 262 Hz and 266 Hz 262 Hz and 272 Hz