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What is the frequency range of sound that humans can hear?
What is the frequency range of sound that humans can hear?
What is the primary factor that loudness of a sound depends on?
What is the primary factor that loudness of a sound depends on?
What is the range of frequencies below 20 Hz called?
What is the range of frequencies below 20 Hz called?
What happens when the acoustic impedance of two media are equal?
What happens when the acoustic impedance of two media are equal?
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What is one clinical application of ultrasound?
What is one clinical application of ultrasound?
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What is the purpose of the bell in a stethoscope?
What is the purpose of the bell in a stethoscope?
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What is the unit of measurement for sound intensity?
What is the unit of measurement for sound intensity?
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What is the primary use of an audiogram?
What is the primary use of an audiogram?
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What is the ratio of sound intensity to a reference intensity called?
What is the ratio of sound intensity to a reference intensity called?
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What is the effect of a large difference in acoustic impedance between two media?
What is the effect of a large difference in acoustic impedance between two media?
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What characteristic of sound can the human ear distinguish?
What characteristic of sound can the human ear distinguish?
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What is the medical application of infrasound in the study of heart mechanical function?
What is the medical application of infrasound in the study of heart mechanical function?
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What determines the natural frequency of a stethoscope bell?
What determines the natural frequency of a stethoscope bell?
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What is the purpose of selecting a specific bell size and diaphragm tension in a stethoscope?
What is the purpose of selecting a specific bell size and diaphragm tension in a stethoscope?
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What is the purpose of measuring sound intensity?
What is the purpose of measuring sound intensity?
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What is the term for the degree of sensation of sound produced in the ear?
What is the term for the degree of sensation of sound produced in the ear?
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What is the effect of intense infrasonic noise on the human body?
What is the effect of intense infrasonic noise on the human body?
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What is the term for the measurement of the micro-vibrations produced by the heart contraction and blood ejection into the vascular tree?
What is the term for the measurement of the micro-vibrations produced by the heart contraction and blood ejection into the vascular tree?
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What happens when there is a sign change in the reflected wave?
What happens when there is a sign change in the reflected wave?
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What is the term for the ratio of reflected or transmitted waves to incident waves?
What is the term for the ratio of reflected or transmitted waves to incident waves?
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What is the term for the number of rarefactions and compressions that occur per unit time in a sound wave?
What is the term for the number of rarefactions and compressions that occur per unit time in a sound wave?
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What is the speed of sound dependent on?
What is the speed of sound dependent on?
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What is the definition of a sound wave?
What is the definition of a sound wave?
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What is the mathematical representation of the wavelength of a sound wave?
What is the mathematical representation of the wavelength of a sound wave?
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What is the term for the distance between successive compressions and rarefactions in a sound wave?
What is the term for the distance between successive compressions and rarefactions in a sound wave?
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How does the speed of sound change in different mediums?
How does the speed of sound change in different mediums?
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What is the mathematical representation of the frequency of a sound wave?
What is the mathematical representation of the frequency of a sound wave?
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What is the term for the energy transferred per unit time in a sound wave?
What is the term for the energy transferred per unit time in a sound wave?
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What is the relationship between frequency and wavelength of a sound wave?
What is the relationship between frequency and wavelength of a sound wave?
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What is the unit of measurement for the velocity of sound?
What is the unit of measurement for the velocity of sound?
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What is the primary characteristic of infrasound that allows it to travel long distances without losing much power?
What is the primary characteristic of infrasound that allows it to travel long distances without losing much power?
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What is the primary difference between ultrasound and infrasound?
What is the primary difference between ultrasound and infrasound?
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What is the term for the study of heart mechanical function using infrasound?
What is the term for the study of heart mechanical function using infrasound?
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What is the primary application of ultrasound in clinical medicine?
What is the primary application of ultrasound in clinical medicine?
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What is the effect of intense infrasonic noise on the human body?
What is the effect of intense infrasonic noise on the human body?
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What is the primary characteristic of a sound wave that allows it to transfer energy without transferring matter?
What is the primary characteristic of a sound wave that allows it to transfer energy without transferring matter?
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What is the term for the local increase or decrease of pressure relative to atmospheric pressure in air?
What is the term for the local increase or decrease of pressure relative to atmospheric pressure in air?
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What is the primary reason why infrasound can travel through most media?
What is the primary reason why infrasound can travel through most media?
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Study Notes
Characteristics of Sound
- Loudness (or volume) is the degree of sensation of sound produced in the ear, dependent on its intensity.
- Pitch refers to whether a sound is high (sharp) or low.
Sound Reflection and Transmission
- When a sound wave is applied perpendicularly to the interface between two media with different acoustic impedance (Z1 and Z2), a portion of the wave passes through, and another portion is reflected.
- The ratio of reflected (Iref) or transmitted (Itran) waves to the incident wave (Iin) can be measured.
- If Z1 = Z2, there is no reflected wave, and transmission to the second medium is complete.
- If Z2 < Z1, there is a phase change of the reflected wave.
- If ∆Z is large, there is high reflection and low transmission (mismatching).
Audiogram
- An audiogram for the normal human ear shows the faintest sounds that can be heard (hearing threshold) and the loudest sounds that can be heard without pain (pain threshold).
- The sound of 1000Hz is barely audible.
Applications of Audible Sound in Medicine
- Stethoscopes are diagnostic instruments that amplify sounds made by the body from the heart, lungs, or other body sites.
- The bell of a stethoscope serves as an impedance matcher between the body and the air in the tube, requiring resonance of the sound frequency with the bell membrane.
- The natural frequency of the bell depends on the diameter and tension of the diaphragm.
Sonic Spectrum
- Sonic spectrum can be classified into three frequency ranges: infrasound, audible sound, and ultrasound.
- The human ear can hear sounds in the range of roughly 20 Hz to 20 KHz.
Infrasound
- Infrasound refers to sound frequencies below 20 Hz.
- It is produced by natural phenomena like earthquake waves and atmospheric pressure changes.
- Infrasound can travel long distances without losing much power and can travel through most media, making its effects difficult to minimize.
- Intense infrasonic noise can produce respiratory impairment, aural pain, fear, visual hallucinations, and chills.
- Infrasound can be used in the study of heart mechanical function, revealed by the seismocardiogram.
Ultrasound
- Ultrasound is the frequency range above 20 KHz.
- Ultrasound is used clinically in various specialties, providing more information than X-rays and being less hazardous for the fetus.
Intensity of a Sound Wave
- The intensity I of a sound wave is the energy carried by the wave per unit area and per unit time (in units W/m²).
- Intensity can be expressed by the maximum change in pressure.
Sound Intensity Level (Ratio)
- The absolute value of sound intensity (I) cannot be measured; instead, it can be compared to a reference intensity (I₀).
- The intensity ratio is the ratio of the sound intensity to the reference intensity.
Effect of Sound on Human Hearing
- The human ear can distinguish two characteristics of sound: loudness and pitch.
General Properties of Sound
- A sound wave is the pattern of disturbance caused by the energy traveling away from the source of the sound.
- Sound is a mechanical disturbance that propagates through an elastic material medium with some definite velocity.
- In air, sound can be defined as a local increase (compression) or decrease (rarefaction) of pressure relative to atmospheric pressure.
- Sound travels fastest in solids, relatively slower in liquids, and slowest in gases.
- The sound speed is given by: v = √(B/ρ), where B is the bulk modulus and ρ is the density of the medium.
- The frequency of a sound wave is the number of rarefactions and compressions that occur per unit time, mathematically represented as: f = 1/T.
- The wavelength of a sound wave is the distance between successive compressions and rarefactions, mathematically represented as: λ = v/f.
Sound Waves
- Sound waves are patterns of disturbance caused by energy traveling away from the source of the sound.
- Sound waves transfer energy without transferring matter.
- Sound can be defined as a mechanical disturbance from a state of equilibrium that propagates through an elastic material medium with a definite velocity.
Classification of Sound Waves
- Sound waves can be classified into three frequency ranges:
- Infrasound: below 20 Hz
- Audible sound: between 20 Hz and 20 KHz
- Ultrasound: above 20 KHz
Human Hearing Range
- The human ear can hear sounds in the range of roughly 20 Hz to 20 KHz.
Infrasound
- Infrasound refers to sound frequencies below the normal hearing range (less than 20 Hz).
- It is produced by natural phenomena like earthquake waves and atmospheric pressure changes.
- Infrasound can travel long distances without losing much power due to its low absorption and large wavelength.
- It can travel through most media, making its effects difficult to minimize.
- Intense infrasonic noise can produce clear symptoms including:
- Respiratory impairment
- Aural pain
- Other effects of infrasound may include:
- Fear
- Visual hallucinations
- Chills
- Infrasound can also be used in the study of heart mechanical function, revealed by the seismocardiogram.
Ultrasound
- Ultrasound refers to sound frequencies above 20 KHz.
- Ultrasound is used clinically in a number of specialties.
- It often gives more information than an X-ray and is less hazardous for the fetus.
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Description
This quiz covers the fundamentals of sound properties, including loudness and pitch, as well as sound reflection and transmission at interfaces between different media.
