Science: Sound

Echolocation

-process by which some animals, like a bat, send out high frequency sound waves and detect the reflected waves, in order to navigate and find prey

Elasticity

the ability of particles to bounce back to their original positions in a material

Sonar

the process by which sound waves are sent out into water to calculate the position of under water objects based on how quickly the reflected waves are detected

amplitude

a mesure of how much the particles of a medium are vibrating

What does sound travel better in/

Sound travels faster in hotter objects then colder objects

Using reflected sound

-sonar is basically the artificial version of echolocation in which sound waves are sent through water to locate underwater objects or to map the terrain under the water based on the time it takes sound waves to reflected from the targeted objects. -Cameras also use high frequency sound waves to calculate distance so that the carmen can adjust its focus correctly

Factors which determine frequency

-all objects vibrate when the particles are disturbed. -the frequency of the vibration depends on the object -longer vibration=lower frequency -quicker vibration=higer frequency -tension, thickness, and temperature affect the way an object vibrates -increasing tension and lowering the thickness and the density of the strings increases pitch=the strings vibrate faster than looser, thicker and denser strings

Amplitude

-amplitude is the maximum displacement of the particles form their original positions. -the more energy the wave carries the bigger the amplitude -as sound waves spread the amplitude decreases

Pitch

-describes how high or low a sound appears to be -pitch depends on frequency of the sound wave

Measure of loudness

-intensity is the measured in units called decibels -Humans ear detects range of sound intensities, on a decibel scale of multiples of 10. -level we can just hear sound is called threshold of hear(0db) -sound proofing materials only absorb some sound as well as decreases the amplitude

What does the speed of sound depend on?

-mass of the particles -temperature of the object -strong forces of the particles(elasticity)

Loudness

-measured in two factors -the energy involved in making the sound wave -distance from the source of the sound -measure the intensity of the sound that we detect

The speed of sound

-sound travels better through solids, slower in liquids and slowest in gases -particles in solid have strong forces, make particles bounce back quickly after being disturbed -sound travels in materials with high elasticity -speed of sound travels differently in solids and liquids because of mass -particles with more energy can bounce back and move out of place quickly

How sound travels

-sound waves are caused by a vibration and carry energy -Sound waves must have a medium to travel through -sound waves travel by disturbing the particles in the medium. -sound waves push the particles of the medium, closer together, the particles that have been disturbed then push neighboring particles, before bouncing back into their original positions -as sound travels through a medium such as air, the particles are pushed together in some areas and spread further apart in others -This produces a pattern of compressions and rarefactions -as sound waves travel through air, particles of the air are being pushed together and are bouncing apart. this creates areas of higher and lower pressure in the air. -^sound waves=pressure waves

Concave surfaces

-sound waves bounce off and are focused inward toward a focal point

Hearing reflected sound

-sound waves spread out in all directions in a room -some sound goes directly to your ears and some sound bounces off of the walls then goes your ears shortly after the original sound -sound needs to be .1 seconds apart for our brains to recognize them as 2 separate sounds -to hear an echo, the sound waves must reflect off of a surface 17m away from the source of the sound (works best if sound waves can't spread out too much)

Convex surfaces

-spread out sound waves. This is important in places where concerts are held so every listener will experience the sound coming form every direction

Reflection VS. Absorption

-when sound hits a material some energy is reflected and some is absorbed -Most energy is reflects and little passes through the walls -empty rooms seem loud because a lot of sound is reflecting off of the hard walls and floors -when a room has furniture, some of the energy of the sound wave is absorbed by the furniture making the room seem quieter -When sound waves reflect over and over again it is called reverberation -no reflection=sound feels "dead" -too much reverberation=sound becomes unclear and garbled

Reflection of sound

-when sound waviness hit a surface they bounce off -some energy is transferred or absorbed into the material

Frequency

Frequency is the number of vibrations by the medium per second -it is measured in Hertz. -High pitch sounds have a high frequency humans can hear from 20 to 20,000 -frequencies higher then humans can hear are called ultrasound -frequencies lower are called infrasound

Effect of distance

Intensity is a measure of how much energy passes through a unit of area each second -intensity of sound decreases with distance -As sound travels it spreads out -The total energy of the sound wave stays the same, but as the sound waves get further apart, less energy passes through each cm2 each second

middle ear

On the other side of the eardrum are the three tiny bones of the middle ear, the hammer, the anvil, and the stirrup. They are named for their shapes. Vibrations in the eardrum are passed to the hammer, which transmits them to the anvil, which makes the stirrup vibrate against the oval window of the cochlea. Bone is a very good conductor of vibrations, and the bones of the middle ear are specially arranged so that they can amplify (make louder) very quiet sounds. On the other hand, if things get too loud, tiny muscles in your middle ear can relax the eardrum a bit. A relaxed eardrum doesn't vibrate as much (think of a relaxed rubber band as opposed to a taut one), and this helps to keep things from getting damaged.

Reverberation

repeated reflections of a sound wave which make the sound audible for longer

Cochlea

The cochlea is a fluid-filled spiral (shaped something like a snail shell) about the size of a pea. Vibrations in the stirrup bone make waves in the fluid that travel down the spiral. In the fluid, in a long strip called the organ of Corti follows the spiral. This organ is covered with (about 20,000) tiny, incredibly sensitive hair-like sensors that are waving around inside the Cochlear fluid. Each of these sensors is a nerve ending that is picking up specific information about the vibrations in the fluid. At the end of the organ of Corti, the nerves are bundled together as the auditory nerve, which brings the information to the brain. NOTE: The fragile, sensitive sensors on the organ of Corti would never stand up to the rough conditions in the ear canal but they are somewhat protected by the fluid in the cochlear. Even protected in the Cochlear fluid, they don't last forever, especially the ones that can sense the highest-frequency vibrations. That is why most people begin to lose their sense of hearing as they grow older.

main parts of the ear

The ear has three main sections. In the outer ear, the sound waves are still moving in air. In the middle ear, the sound waves are being conducted by three small bones. In the inner ear, the waves are moving through the fluid-filled cochlea.

the ear

The ear is the sense organ that picks up sound waves from the surrounding air and turns them into nerve impulses that can be sent to the brain. The sound waves carry lots of information - language, music, and noises - all mixed up together. The task of the ear is to turn the signals in these waves of bouncing air molecules into electrical nerve signals, while keeping as much of the information in the signal as possible. (Then it's the brain's job to sort the signals and make sense out of them.) It's not easy to turn one kind of signal into another kind without losing information, but the ear is well designed for the task.

the outer ear

The part of the human ear that you can see is simply a sound wave collector. Its shape helps to funnel the sound waves into the auditory canal (or ear canal) so that you get plenty of signals from even soft sounds, particularly ones from the direction that you are looking at. At the other end of the ear canal is the eardrum (or tympanic membrane). This is a membrane that is stretched tight, like the membranes on the tops of drums (including tympani). And thin, taut membranes are very good at vibrating, which is why they can be found both on drums and inside ears. The eardrum picks up the vibrations in the ear canal and vibrates with them.

What can't sound travel through?

Vacuums -because no particles

the ear part 2

When something vibrates, the vibrations can travel as waves through solids, liquids, and gases. Even animals that have no ears can often feel these vibrations. But in order to understand language and hear music, the brain has to be given more information than just "there's a vibration". It needs to know the frequency and amplitude of all the waves that the ear is collecting. Interestingly, the ear sends this information to the brain very accurately by turning the sound waves in the air (vibrations in a gas) into vibrations in bones (solid), and then into waves in a fluid in the inner ear (a liquid), before they become (electrical) nerve signals. This might seem like a lot of unnecessary translation, but it allows the sense of hearing to be both sturdy and very sensitive, as explained below.

Natural frequencies

every object has natural frequencies= frequency or set of frequency at which it will vibrate -The lowest frequency is called the fundamental -has longest wavelength of natural frequencies and greatest amplitude -other frequencies at which an object will vibrate are called over tones

Natural frequency

frequencies at which an object will automatically vibrate when the objects is stuck

The Doppler effect

if sound waves are produced by an object which is moving toward you, the sound waves reach more frequently then they would if the object was standing still. you hear this as a higher pitched sound

intensity

the energy passing through an area per second

fundamental

the lowest natural frequency of an object

frequency

the number of vibrations per second

Compression

the part of a sound wave where particles are closer together then when the wave is not passing

rarefaction

the part of a sound where particles are more spread out

decibel

unit in which the intensity of the sound is measured