Sound in Medicine PDF

Sound in Medicine Frequency Sound in Medicine Sound: Is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a medium such as air or water. In physiology and psychology, sound is the reception of such waves and their perception by the brain. Sound...

Sound in Medicine Frequency Sound in Medicine Sound: Is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a medium such as air or water. In physiology and psychology, sound is the reception of such waves and their perception by the brain. Sound in Medicine Physics of sound: Sound can propagate through compressible media such as air, water and solids as longitudinal waves and also as a transverse wave in solids. The sound waves are generated by a sound source, such as the vibrating diaphragm of a stereo speaker. The sound source creates vibrations in the surrounding medium. As the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound, thus forming the sound wave. At a fixed distance from the source, the pressure, velocity, and displacement of the medium vary in time. Sound in Medicine Physics of sound: At an instant in time, the pressure, velocity, and displacement vary in space. Note that the particles of the medium do not travel with the sound wave. This is intuitively obvious for a solid, and the same is true for liquids and gases (that is, the vibrations of particles in the gas or liquid transport the vibrations, while the average position of the particles over time does not change). During propagation, waves can be reflected, refracted, or attenuated by the medium. The behavior of sound propagation is generally affected by three things: 1. A complex relationship Between the density and pressure of the medium. This relationship, affected by temperature, determines the speed of sound within the medium. Sound in Medicine Physics of sound: The behavior of sound propagation is generally affected by three things: 2. Motion Of the medium itself. If the medium is moving, this movement may increase or decrease the absolute speed of the sound wave depending on the direction of the movement. For example Sound moving through wind will have its speed of propagation increased by the speed of the wind if the sound and wind are moving in the same direction. If the sound and wind are moving in opposite directions, the speed of the sound wave will be decreased by the speed of the wind. 3. The viscosity Of the medium. Medium viscosity determines the rate at which sound is attenuated. For many media, such as air or water, attenuation due to viscosity is negligible. Sound in Medicine Physics of sound: When sound is moving through a medium that does not have constant physical properties, it may be refracted (either dispersed or focused). The mechanical vibrations that can be interpreted as sound are able to travel through all forms of matter: gases, liquids, solids, and plasmas. The matter that supports the sound is called the medium. Sound cannot travel through a vacuum Sound wave properties and characteristics: Spherical compression (longitudinal) waves Sound in Medicine Figure 1. The two fundamental elements of sound; Pressure and Time Sound in Medicine Figure 2. Sinusoidal waves of various frequencies; the bottom waves have Higher frequencies than those above. The horizontal axis represents time. Sound in Medicine Physics of sound: Although there are many complexities relating to the transmission of sounds, at the point of reception (i.e. the ears), sound is readily dividable into two simple elements: pressure and time. These fundamental elements form the basis of all sound waves. They can be used to describe, in absolute terms, every sound we hear. Figure 1 shows a 'pressure over time' graph of a 20 ms recording of a clarinet tone) Sound in Medicine Physics of sound: However, in order to understand the sound more fully, a complex wave such as this is usually separated into its component parts, which are a combination of various sound wave frequencies (and noise). Figure 2 shows an example of a series of component sound waves such as might be seen if the clarinet sound wave (see above) was broken down into its component sine waves, but with the lower frequency components removed (the frequency ratios shown in figure 2 are too close together to be low frequency components of a sound). Sound waves are often simplified to a description in terms of sinusoidal plane waves, which are characterized by these generic properties: 1. 2. 3. 4. 5. Frequency, or its inverse, the Wavelength Amplitude Sound pressure / Intensity Speed of sound Direction Sound in Medicine Physics of sound: Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure, the corresponding wavelengths of sound waves range from 17 m to 17 mm. Sometimes speed and direction are combined as a velocity vector; wave number and direction are combined as a wave vector. Transverse waves, also known as shear waves, have the additional property, polarization, and are not a characteristic of sound waves Sound in Medicine Speed of sound The speed of sound depends on the medium that the waves pass through, and is a fundamental property of the material. The first significant effort towards the measure of the speed of sound was made by Newton. He believed that the speed of sound in a particular substance was equal to the square root of the pressure acting on it (STP) divided by its density. 𝒄= 𝒑  Sound in Medicine Speed of sound This was later proven wrong when found to incorrectly derive the speed. French mathematician Laplace corrected the formula by deducing that the phenomenon of sound travelling is not isothermal, as believed by Newton, but adiabatic. He added another factor to the equation-gamma-and multiplied  to 𝒑  , thus coming up with the equation 𝒄 = Since K=  , The final equation came up to be 𝒄 = 𝒑 ..  𝑲  which is also known as the Newton-Laplace equation. Sound in Medicine Speed of sound In this equation, K = elastic bulk modulus, c = velocity of sound, and = density. Thus, the speed of sound is proportional to the square root of the ratio of the bulk modulus of the medium to its density. Those physical properties and the speed of sound change with ambient conditions. For example, the speed of sound in gases depends on temperature. Sound in Medicine Speed of sound For example, the speed of sound in gases depends on temperature. In 20 °C (68 °F) air at sea level, the speed of sound is approximately 343 m/s. In fresh water, also at 20 °C, the speed of sound is approximately 1,482 m/s (5,335 km/h; 3,315 mph). In steel, the speed of sound is about 5,960 m/s (21,460 km/h; 13,330 mph). The speed of sound is also slightly sensitive, being subject to a second-order Anharmonic effect, to the sound amplitude, which means that there are non-linear propagation effects, such as the production of harmonics and mixed tones not present in the original sound. Sound in Medicine Speed of sound Note: An isothermal process is a change of a system, in which the temperature remains constant: ΔT = 0. This typically occurs when a system is in contact with an outside thermal reservoir (heat bath), and the change occurs slowly enough to allow the system to continually adjust to the temperature of the reservoir through heat exchange. In contrast, an adiabatic process is where a system exchanges no heat with its surroundings (Q = 0). In other words, in an isothermal process, the value ΔT = 0 but Q ≠ 0, while in an adiabatic process, ΔT ≠ 0 but Q = 0. Sound in Medicine Sound : facts What is sound ? Sound is a kind of energy created when something vibrates. When this vibration reaches an ear, it is translated into what we recognize as a sound. Sound vibration must travel through matter. This is typically air. When you say, "Hello,“ to a friend, the air parts (called molecules) vibrate in small waves which travel to the friend and they hear the word "Hello. Sound can also travel through other matter. Tap on the table, Do you hear that? Your tapping caused waves to travel through the material of the table and then through the air to your ears Sound in Medicine Sound : facts What is sound ? Sound in Medicine Sound : facts What is sound ? Ask a friend to touch the top of the table while you tap, They can also feel the waves. note: Sound cannot travel through a vacuum. A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in. Sound in Medicine Sound : facts Sound travels in waves: Sound in Medicine Sound : facts What is sound ? Sound waves usually travel through air or water, but they can also travel through solids too, like walls or furniture. Sound waves use the matter to move the vibrations. Sound in Medicine Sound : facts How do vibrations work? All matter is made of small particles called molecules. When a sound is created, the molecules bump into one another in a pattern. Those molecules bump into the next set of molecules, which in turn bump into the next molecules. This continues until the energy runs out. If you have ever thrown a rock into a pond, you have seen the rings of water waves that move out from the place where the rock landed. This is much the same way that sound waves travel. Sound in Medicine Sound : facts Frequency All sound waves move much the same as a wave in water. There are high spots known as crests and low spots called troughs. The distance between a crest and the next crest is called the frequency. The number of crests that move past a given point in a second is called the frequency. To the human ear, we perceive this as pitch. Sound in Medicine Sound : facts Frequency A child screaming, for example, has a high pitch because the waves are moving quickly A big drum would have a low sound because the waves are moving slowly. Notes on a piano each sound different because they each vibrate at a different frequency. Sound in Medicine Sound : facts Amplitude Because sound waves are a kind of energy, they also put out a certain amount of pressure. This pressure can be measured as volume or amplitude. If you could look at a sound wave, you would see that the crests get taller as the amplitude increases. Sound in Medicine Sound : facts Echoes An echo is the reflection of sound waves bouncing off of a surface and then returning to the sender. Echoes can often be heard in a gym, in a canyon or a concert hall. The sound waves must have some object to bounce off of, the bigger the better. So the walls of a canyon make a great surface for the waves to hit and then return a few minutes later to be heard as an echo. Sound in Medicine Sound : facts Decibels The unit of measuring the loudness of a sound Unite of measurement for gauging the intensity of sound. Sound in Medicine Using Sound: People and animals use sound for communication and as a tool Electrocardiogram: Doctors use sound waves to identify the health of a person's heart Sonar : Geologists use sound waves to identify geologic features under the surface of the earth. Waves are sent through the ground and they bounce back to special sensing devices that measure the materials under the earth. Echolocation : bats, birds, dolphins, and whales use sound to navigate their way around. Sound in Medicine Using Sound: Ultrasound : Doctors use ultrasound to look into the body using sound waves. It is totally painless and can give experts an opportunity to see if a baby is developing correctly as well as for other purposes. Ultrasonic cleaners : Dentists use high frequency sound to clean people's teeth. The sound literally shatters the plaque right off the teeth without hurting the gums. Sound in Medicine Using Sound: Extracorporeal Shock Waves : Sound waves have been used to shatter kidney and gall bladder stones so that surgery can be avoided. Doppler: The National Weather Service uses Doppler sound waves to measure weather conditions. Sound in Medicine Doppler Effect When sound is traveling, a curious effect can take place. All of us have experienced hearing the sound of a train going by or a fire engine with its siren screaming. When the sound is in the distance it has one pitch, but as it gets closer the pitch goes up. Does the sound of the moving object actually change? No, sound waves created by the train or fire engine do not change for people riding in the vehicles. They only change for outside observers as the vehicle moves closer and then move on past. This change is called the Doppler Effect. Sound in Medicine Doppler Effect The Doppler Effect happens when the sound waves from the moving object are moving toward the observer. As the object moves toward the observer, the distance between them gets shorter. Because this distance is decreasing, the sound waves are being compressed between the two. As the object moves past the observer, the distance increases and it takes longer for the sound to reach them. The sound then seems lower. The actual frequency of the sound wave never actually changes; it just seems that way to the observer. Sound in Medicine Lightning and Thunder Lightning is the light created by a static charge - a light wave. Thunder is the sound created by the quick movement of the heated air - a sound wave. Light travels at 186,000 miles per second (299792.458 km/s). The speed of sound can vary depending upon many properties, including temperature and humidity, but 760 miles per hour (340 m/s) on a normal spring day is widely accepted. This basically means that light can travel faster than sound or that the flash of the lightning will be observed first and the sound will be heard after the flash. To find out how far away the lighting is from you, count the seconds from the flash to the sound. Then divide the number of seconds by 5 to determine how far away in miles the lightning hit. Sound in Medicine Lightning and Thunder Sound in Medicine How do we hear? Hearing is all about the vibrations of sound as they hit our ears. Inside the outer ear - or that part we all see - is a complex series of ear parts that also vibrate when sound hits them. The eardrum is a drum shaped part that vibrates with the sound waves as they hit it. Behind the eardrum is the snail shaped piece that also regulates balance called the cochlea and three small bones: the hammer, the anvil, and the stirrup. As sound vibrations travel this route of ear parts, it is transferred from piece to piece until it sends signals to the nerves that take the message to the brain. Sound in Medicine Ultra sounds are sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is no different from 'normal' (audible) sound in its physical properties, except in that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz (20,000 hertz) in healthy young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz. Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances. Ultrasound imaging or sonography is often used in medicine Sound in Medicine Ultra sounds Sound in Medicine Ultra sounds Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz." low bass notes Animals and Medical and destructive chemistry Diagnostic and NDE Sound in Medicine Humans The upper frequency limit in humans (approximately 20 kHz) is due to limitations of the middle ear. Auditory sensation can occur if high‐intensity ultrasound is fed directly into the human skull and reaches the cochlea through bone conduction, without passing through the middle ear. Children can hear some high-pitched sounds that older adults cannot hear, because in humans the upper limit pitch of hearing tends to decrease with age. Sound in Medicine Sonar: Originally an acronym for sound navigation and ranging A common use of ultrasound is in underwater range finding; this use is also called Sonar. An ultrasonic pulse is generated in a particular direction. If there is an object in the path of this pulse, part or all of the pulse will be reflected back to the transmitter as an echo and can be detected through the receiver path. By measuring the difference in time between the pulse being transmitted and the echo being received, it is possible to determine the distance. The measured travel time of Sonar pulses in water is strongly dependent on the temperature and the salinity of the water. Ultrasonic ranging is also applied for measurement in air and for short distances. Sound in Medicine Humans medicine Medical sonography (ultrasonography): Is an ultrasound-based diagnostic medical imaging technique used to visualize muscles, tendons, and many internal organs, to capture their size, structure and any pathological lesions with real time tomographic images. Ultrasound has been used by radiologists and sonographers to image the human body for at least 50 years and has become a widely used diagnostic tool. The technology is relatively inexpensive and portable, especially when compared with other techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT). Ultrasound is also used to visualize fetuses during routine and emergency prenatal care. Such diagnostic applications used during pregnancy are referred to as obstetric sonography. Sound in Medicine Humans medicine As currently applied in the medical field, properly performed ultrasound poses no known risks to the patient. Sonography does not use ionizing radiation, and the power levels used for imaging are too low to cause adverse heating or pressure effects in tissue. Sonogram of a fetus at 14 weeks (profile) Sound in Medicine Physical therapy Ultrasound has been used since the 1940s by physical and occupational therapists for treating connective tissue: ligaments, tendons, and fascia (and also scar tissue). Conditions for which ultrasound may be used for treatment include the follow Examples: ligament sprains, muscle strains, tendonitis, joint inflammation, plantar fasciitis, metatarsalgia, facet irritation, impingement syndrome, bursitis, rheumatoid arthritis, osteoarthritis, and scar tissue adhesion. Sound in Medicine Biomedical applications Ultrasound also has therapeutic applications, which can be highly beneficial when used with dosage precautions. Relatively high power ultrasound can break up stony deposits or tissue, accelerate the effect of drugs in a targeted area, assist in the measurement of the elastic properties of tissue, and can be used to sort cells or small particles for research. Sound in Medicine Physics of the Ear and hearing: The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts- the outer ear, middle ear and the inner ear The ear has external, middle, and inner portions. The outer ear is called the pinna and is made of ridged cartilage covered by skin. Sound funnels through the pinna into the external auditory canal, a short tube that ends at the eardrum (tympanic membrane). Sound in Medicine Physics of the Ear and hearing: Sound causes the eardrum and its tiny attached bones in the middle portion of the ear to vibrate, and the vibrations are conducted to the nearby cochlea. The spiral-shaped cochlea is part of the inner ear; it transforms sound into nerve impulses that travel to the brain. The fluid-filled semicircular canals (labyrinth) attach to the cochlea and nerves in the inner ear. They send information on balance and head position to the brain. The Eustachian (auditory) tube drains fluid from the middle ear into the throat (pharynx) behind the nose Sound in Medicine Anatomy of the ear Sound in Medicine Anatomy of the ear The ear is made up of three parts: the outer, middle, and inner ear. All three parts of the ear are important for detecting sound by working together to move sound from the outer part through the middle and into the inner part of the ear. Ears also help to maintain balance. Sound in Medicine Anatomy of the ear The Outer ear : The outer ear includes: 1. Auricle : cartilage covered by skin placed on opposite sides of the head. 2. Auditory canal :also called the ear canal. 3. Eardrum outer layer : also called the tympanic membrane. The outer part of the ear collects sound. Sound travels through the auricle and the auditory canal, a short tube that ends at the eardrum. Sound in Medicine Anatomy of the ear The Middle Ear: The middle ear includes: 1. Eardrum 2. Cavity : also called the tympanic cavity 3. Ossicles : 3 tiny bones that are attached: Malleus (or hammer) long handle attached to the eardrum Incus (or anvil) the bridge bone between the malleus and the stapes Stapes (or stirrup) the footplate; the smallest bone in the body Sound in Medicine Anatomy of the ear The Middle Ear: Sound entering the outer ear travels through the middle ear and causes the eardrum and ossicles in the middle ear to vibrate. As it travels, it amplifies (becomes louder) and changes from air to liquid Sound in Medicine Anatomy of the ear The Inner Ear: The inner ear includes: 1. Oval window : connects the middle ear with the inner ear 2. Semicircular ducts : filled with fluid; attached to cochlea and nerves; send information on balance and head position to the brain 3. Cochlea spiral-shaped organ of hearing; transforms sound into signals that get sent to the brain 4. Auditory tube : drains fluid from the middle ear into the throat behind the nose Sound in Medicine Anatomy of the ear The Inner Ear: When the stapes moves, it pushes the oval window, which then moves the cochlea. The cochlea takes the fluid vibration of sounds from the surrounding semicircular ducts and translates them into signals that are sent to the brain by nerves like the vestibular nerve and cochlear nerve.