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Questions and Answers
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 range of frequencies below 20 Hz called?
What happens when the acoustic impedance of two media are equal?
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What is one clinical application of ultrasound?
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What is the purpose of the bell in a stethoscope?
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What is the unit of measurement for sound intensity?
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What is the primary use of an audiogram?
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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?
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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?
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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?
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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?
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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?
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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?
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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?
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What is the definition of a sound wave?
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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?
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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?
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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?
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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?
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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?
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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?
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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?
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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.
