How do they work?
Sound is something humans cannot see so it can be somewhat of a complicated concept. Sound is produced when something causes a vibration, which creates a sound wave that travels through the air. There are many things that can affect the way perceive sound waves. One thing that can really affect a sound wave is other sound waves. If the sound waves are out of phase, the two sound waves will destructively interfere with each other making the two waves cancel each other out.
There are two different types of headphones are dynamic and electrostatic. Dynamic headphones are much more popular because they are much cheaper to produce. Dynamic headphones work just like your standard loud speakers. At the front of a dynamic speaker there is a cone. This cone is called the diaphragm and it is usually made out a
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lightweight material like paper, plastic, or lightweight metals.
This part of the speaker will flex in and out causing air to be pushed in out creating a sound wave. The outer rim of the cone will be permanently connected to the headphone frame, so that only the back, inner part of the cone can move. Behind the diaphragm is the iron coil, which is sometimes called the voice coil. The iron coil is directly connected to the back, inner part of the cone and the two pieces are free to move together. The iron coil is connected to the two wires that run from the music-playing device to the speaker. Directly behind the iron coil is a permanent magnet, which is sometime called the field magnet. The permanent magnet is the only part of the speaker that does not move in and out with cone. When electricity flows through the wires and iron coil the electricity create an electromagnet. An electro magnet acts just like a permanent
magnet as long as there is electric current going through the coil. The iron coil will then be attracted to the field magnet pulling the cone towards the magnet (back of the headphone). The current then stops going through the iron coil causing the cone to retract and vibrate. This is happening over two thousand times a second. The Mp3 or cd that is playing the music will output the necessary amounts of electricity and at the right time to create the frequencies of sound that make up your music. Electrostatic headphones are cost much more than dynamic headphones to create, but are said to create a better sound quality. Electrostatic headphones require an amplifier to create an electrical field. This electric field will cause an electrically charged diaphragm to move in and out. The diaphragm is suspended between perforated metal plates called electrodes. Electrostatic headphones are often a rectangular shape compared to the round shape of a dynamic headphone because it is easer to make these metal plates square rather than round. When the diaphragm moves in and out it draws air through the perforated metal plates and generates a sound wave. Unlike dynamic headphones the only part that moves on the electrostatic speaker is the thin diaphragm. This means there is a lot less weight moving within the speaker, which means the diaphragm can move much faster allowing the headphones to have a frequency response well above the human audible limit of 20kHz. The result of having a high frequency response means there is less distortion in the different frequencies, which results in better sound quality. One interesting fact about electrostatic headphones is that they are powered anywhere from 100volts to 1000 volts. These high voltages seem like they could be very dangerous, but to keep these headphones safe for humans, manufactures place resistors into the circuit to keep the fault current at a safe level. Headphone manufactures have recently started to use noise-canceling technology to help reduce the ambient noise in the room. Ambient noise is something that will always be around in the 21st century whether it is the baby screaming in the plane seat next to you or just the sound of the air conditioning running. The first way headphone manufacturers have lessened the affect of ambient noise is passive noise control. Passive noise control is literally blocking the sound waves from hitting your ear canal. This can be accomplished a few ways, the first being designing the headphone to make a seal around the ear. If there is a tight seal around the ear the ambient sound waves will be reflected off of the outside of the headphones and will not reach the ear. This is one of the reasons why in-ear-earbuds come with different size rubber ear inserts. The second way to block the sound from entering the ear is to use very sound absorbent material around the speaker. The sound will try to pass through the material, but the material will absorb the energy stored in the sound wave and the ambient sound will not reach the ear. The headphones with this type of noise-canceling technology are usually marketed as noise-isolating headphones. Generally noise-isolating headphones can block up to 20 decibels of ambient background noise. The second way headphone manufactures have been deadening ambient noise is using active noise control. Instead of just blocking sound waves from hitting the listener’s ear, active noise control uses destructive interference to cancel out ambient noise. Amar Bose, the founder of the Bose Corporation, first created this technology to help airplane pilots deal with the very loud jet turbine motors on long flights. Active nose control uses a very small microphone very close to the listener’s ear. This microphone will pick up the frequency of the ambient, unwanted noise and the headphones will generate a frequency that is exactly 180 degrees out of phase from the unwanted noise. This frequency called anti-noise is outputted and directly cancels out the unwanted sound. Active noise control headphones can reduce overall noise up to 80 decibels. One downside to listening to audio on headphones is the cord that has to run from you to your device. The wires always get tangled, or they are in your way and you a literally tied to your device. Thanks to all the engineers and researchers who made wireless headphones possible so consumers no longer have to deal with all of that. Most of the wireless headphones in the market today use Bluetooth connectivity to connect to your device wirelessly. To use Bluetooth technology both components must have an antenna-equipped chip that sends and receives signals at a specific frequency. Bluetooth software then interprets the incoming signal and sends them out in ways other devices can read and understand. In the case of headphones, the audio player will send signals to the headphones containing audio files and other indicators like volume and track controls. To pair the two devices together, one device is usually setup as a discoverable device, while the other device will search for devices. Once the two devices are paired together for the first time, they will know to connect to each other based off a unique address within their respective signals. Bluetooth devices have a range of about thirty feet depending on the environment the devices are in. The good part about this somewhat short range is that it prevents massive amounts of conflicting data to interrupt the two communicating devices.
Hearing allows us to take in noises from the surrounding environment and gives us a sense of where things are in relation to us. All those little folds on the outside of the ear, called the tonotopic organization, make it so sound waves in the air are directed to the ear canal, where they can be further processed. Once in the ear, the sound waves vibrate the ear drum, which tell the ear exactly what frequency it is sensing. The vibration of the ear drum is not quite enough to send a signal to the brain, so it needs to be amplified, which is where the three tiny bones in the ear come into play. The malleus or hammer, incus or anvil, and stapes or stirrup amplify this sound and send it to the cochlea. The cochlea conducts the sound signal through a fluid with a higher inertia than air, so this is why the signal from the ear drum needs to be amplified. It is much harder to move the fluid than it is to move the air. The cochlea basically takes these physical vibrations and turns them into electrical impulses that can be sent to the brain. This is...
This may happen unconsciously, as is usually the case with soft background noise such as the whoosh of air through heating ducts or the distant murmur of an electric clothes dryer. Sometimes hearing is done semi-consciously; for instance, the roar of a piece of construction equipment might momentarily draw one's attention. Conscious hearing, or listening, involves a nearly full degree of mental concentration. A familiar instance in which listening takes place would be a casual conversation with a friend or colleague. In such cases, the sound waves entering the ear are transferred to the brain, which then
Sound waves consist of a disturbance of air molecules, the vibrations which pass from molecule to molecules from the speaker to the ear of the listener. The rate at which particles in the medium vibrate in the disturbance is the frequency or pitch of the sound measured in hertz (cycles/sound). As the pitch increases there comes a frequency at about 20kHz when the sound is no longer audible and above the frequency disturbance, this is know as ultrasound. The first major breakthrough in the evolution of high frequency echo-sounding techniques came when the piezo-electric effect in certain crystals was discovered by Pierre and Jacques Curie in Paris in 1880. The turn of the century saw the invention of the Diode (component that restricts the direction of movement, allows an electric current to flow in one direction) and the Triode (type of vacu... ...
The mechanical motions of the ossicles directly vibrate a small membrane that connects to the fluid filled inner ear. From this point, vibration of the connective membrane (oval window) transforms mechanical motion into a pressure wave in fluid. This pressure wave enters and hence passes vibrations into the fluid filled structure called the cochlea. The cochlea contains two membranes and between these two membranes, are specialized neurons or receptors called Hair cells. Once vibrations enter the cochlea, they cause the lower membrane (basilar membrane) to move in respect to the upper membrane (i.e. --the tectorial membrane in which the hair cells are embedded). This movement bends the hair cells to cause receptor potentials in these cells which in turn cause the release of transmitter onto the neurons of the auditory nerve. In this case, the hair cell receptors are very pressure sensitive. The greater the force of the vibrations on the membrane, the more the hair cells bend and hence the greater the receptor potential generated by these hair cells.
First, a discussion of the ear physiology is needed. Vibrating air moving at different frequencies hits the eardrum which causes the middle ear's three bones to move accordingly. The stapes, one of these inner ear bones hits on the oval window of the inner ear, and because the inner ear is filled with fluid, the bulging of the oval window causes this fluid to slosh around. The round window, also in the inner ear, compensates for the increased pressure by bulging outward. The inner ear has two functions, to transduce sound via the cochlea and to maintain a person's vertical position with respect to gravity via the vestibular system (1). . But here, we will only consider the transduction of sound. The cochlea is filled with hair cells that are extremely sensitive and depolarize with only slight perturbations of the inner ear fluid. At the point of depolarization, a neural signal is transmitted and on its way to the brain. This nerve impulse travels to the auditory nerve (8th cranial nerve), passes through the brainstem, and then reaches the branched path of the cochlear nucleus: the ventral cochlear nucleus or the dorsal cochlear nucleus. The nerve signal that passes through the ventral cochlear nucleus will reach the superior olive in the medulla where differences in timing and loudness of sound are compared, and location of the sound's origin is pinpointed (1). The nerve signal that crosses the dorsal cochlear nucleus ultimately is analyzed for sound quality.
Ultrasound is sound waves that have a frequency above human audible. (Ultrasound Physics and Instrument 111). With a shorter wavelength than audible sound, these waves can be directed into a narrow beam that is used in imaging soft tissues. As with audible sound waves, ultrasound waves must have a medium in which to travel and are subject to interference. In addition, much like light rays, they can be reflected, refracted, and focused.
As said above, both light and sound waves have to do with interference. In sound, interference affects both the loudness and amplitude. When two waves’ crests overlap, the amplitude increases. The same is true with the troughs of the waves, which decrease the amplitude.
Sound waves take the form of compressional waves and are caused by vibrations. Sound waves are distinguished by their speed, pitch, loudness and quality (timbre) (Lapp, 2003). There are a few parts of sound waves that we should be familiar with to better be able to understand the physics of music. The crest is the highest point of a wave, while the trough is the lowest. The wavelength of a wave is the distance between two adjacent parts of a wave, like from crest to crest, or from trough to trough....
Sound does however perform much more important, intricate and complex functions than commonly accepted. Sound combines with moving pictures in various ways to create meaning but is diverse and has numerous other uses.
Speaking of how the human ear receives music, sound is produced by vibrations that transmits energy into sound waves, a form of energy in which human ears can respond to and hear. Specifically, there are two different types of sound waves. The more common of the two are the transversal waves, which ...
The ear is looked upon as a miniature receiver, amplifier and signal-processing system. The structure of the outer ear catching sound waves as they move into the external auditory canal. The sound waves then hit the eardrum and the pressure of the air causes the drum to vibrate back and forth. When the eardrum vibrates its neighbour the malleus then vibrates too. The vibrations are then transmitted from the malleus to the incus and then to the stapes. Together the three bones increase the pressure which in turn pushes the membrane of the oval window in and out. This movement sets up fluid pressure waves in the perilymph of the cochlea. The bulging of the oval window then pushes on the perilymph of the scala vestibuli. From here the pressure waves are transmitted from the scala vestibuli to the scala tympani and then eventually finds its way to the round window. This causes the round window to bulge outward into the middle ear. The scala vestibuli and scala tympani walls are now deformed with the pressure waves and the vestibular membrane is also pushed back and forth creating pressure waves in the endolymph inside the cochlear duct. These waves then causes the membrane to vibrate, which in turn cause the hairs cells of the spiral organ to move against the tectorial membrane. The bending of the stereo cilia produces receptor potentials that in the end lead to the generation of nerve impulses.
Sound is made when something vibrates. The vibrating body causes the medium water and air around it to vibrate. Vibrations in the air are traveling longitudinal waves, that we can hear. Sound waves are in areas of high and low pressure called compressions and rarefactions. Lighter areas are low pressure rarefactions and darker areas are high pressure compressions. The wavelength and the speed of the wave figures the pitch, or frequency of sound. Wavelength, frequency, and speed are related by the equation speed means wavelength. Since sound travels at 343 meters per second at standard temperature and pressure speed is a constant. The longer the wavelength, the lower the pitch. The height of the wave is its amplitude. The amplitude shows how
Sound is essentially a wave produced by a vibrating source. This compression and rarefaction of matter will transfer to the surrounding particles, for instance air molecules. Rhythmic variations in air pressure are therefore created which are detected by the ear and perceived as sound. The frequency of a sound wave is the number of these oscillations that passes through a given point each second. It is the compression of the medium particles that actually constitute a sound wave, and which classifies it as longitudinal. As opposed to transverse waves (eg. light waves), in which case the particles move perpendicular to the direction of the wave movement, the medium particles are moving in the same or opposite direction as the wave (Russell, D. A., 1998).
...placing a soft metal core (commonly an iron alloy) inside a coil of wire through which electric current passes in order to produce a magnetic field. The strength and polarity of the magnetic field changes depending on the magnitude of the current flowing through the wire and the direction of the current flow. While there is sufficient flow of current, the core behaves like a magnet; however, as soon as the current stops, the magnetic properties also disappear. Modern devices that make use of electromagnets are the televisions, telephones, computers and electric motors.