Sound in Medicine

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Questions and Answers

What is the formula for the reference intensity (I₀) in sound measurement?

I₀ = I_mim = 10⁻⁶ (W/m²)

I₀ = I_mim = 10⁻¹² (W/m²) (correct)

I₀ = I_mim = 10⁻¹⁸ (W/m²)

I₀ = I_mim = 10⁻²⁴ (W/m²)

What is the term for the degree of sensation of sound produced in the ear?

Frequency

Loudness (correct)

Intensity

Pitch

What happens when the acoustic impedance (Z) of two media is the same?

Partial reflection and partial transmission

Total reflection of the sound wave

No transmission or reflection

Total transmission of the sound wave (correct)

What is the term for the ratio of reflected to incident sound waves?

Reflection coefficient Signup and view all the answers

What is the main component of a modern stethoscope?

Bell with a thin diaphragm Signup and view all the answers

What is the frequency range of infrasound?

Below 20 Hz Signup and view all the answers

What is the term for the range of sound frequencies that can be heard by the human ear?

Audible spectrum Signup and view all the answers

What is the use of infrasound in medical applications?

To study mechanical function of heart Signup and view all the answers

What is the purpose of an audiogram?

To determine hearing thresholds Signup and view all the answers

What is the range of frequencies that a human ear can hear?

Roughly 20 Hz to 20 KHz Signup and view all the answers

What is the effect of intense infrasonic noise on the human body?

Causes respiratory impairment Signup and view all the answers

What happens when there is a large difference in acoustic impedance (ΔZ) between two media?

Total reflection of the sound wave Signup and view all the answers

What is the advantage of ultrasound over X-ray?

It gives more information and is less hazardous for the fetus Signup and view all the answers

What is the term for the ability of a medium to resist the flow of sound energy?

Acoustic impedance Signup and view all the answers

What is the unit of intensity of a sound wave?

W/m^2 Signup and view all the answers

What is the application of audible sound in medicine mentioned in the text?

Stethoscope diagnosis Signup and view all the answers

What is the formula for intensity of a sound wave?

I = p_0^2 / (2Z) Signup and view all the answers

What is the classification of sonic spectrum based on frequency?

Infrasound, audible sound, ultrasound Signup and view all the answers

What is the effect of infrasound on the human body?

Produces respiratory impairment and aural pain Signup and view all the answers

What is the property of infrasound that allows it to travel long distances?

Low absorption and large wavelength Signup and view all the answers

What is the pattern of disturbance caused by energy traveling away from the source of sound?

A mechanical disturbance from a state of equilibrium Signup and view all the answers

What is the relationship between the velocity of sound and the frequency of a sound wave?

Velocity of sound is directly proportional to frequency Signup and view all the answers

What is the wavelength of a sound wave with a frequency of 500 Hz and a velocity of 330 m/s?

0.66 m Signup and view all the answers

What is the frequency of a sound wave with a wavelength of 2.5 m and a velocity of 250 m/s?

100 Hz Signup and view all the answers

What is the term for the number of rarefactions and compressions that occur per unit time in a sound wave?

Frequency Signup and view all the answers

Which of the following is a characteristic of sound waves in solids?

They travel fastest Signup and view all the answers

What is the term for the local increase or decrease in pressure relative to atmospheric pressure in a sound wave?

Compression Signup and view all the answers

Which of the following sound waves will have its crests farther apart from each other?

A wave with a frequency of 100 Hz Signup and view all the answers

What is the equation for the frequency of a sound wave?

f = 1/T Signup and view all the answers

What is the relationship between the intensity of a sound wave and its acoustic impedance?

Intensity is directly proportional to acoustic impedance Signup and view all the answers

Study Notes

General Properties of Sound

A sound wave is a pattern of disturbance caused by 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.

Characteristics of Sound Waves

The frequency of a sound wave is the number of rarefactions and compressions that occur per unit time.
The frequency of a wave is mathematically represented as f = 1/T.
The wavelength of a sound wave is the distance between successive compressions and rarefactions.
The wavelength is mathematically represented as λ = c/f.

Sound Intensity Level [Ratio]

The absolute value of sound intensity (I) cannot be measured, instead, it can be compared with a reference intensity (I0).
The intensity ratio is defined as 10 log (I/I0).

Effect of Sound on Human Hearing

The human ear can distinguish two characteristics of sound: loudness and pitch.
Loudness is the degree of sensation of sound produced in the ear, and it depends 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 will pass through and another one will reflect.
The ratio of reflected (Iref) or transmitted (Itran) and incident waves (Iin) can be measured.
If Z1 = Z2, there is no reflected wave, and transmission to the second medium is complete.
If Z2 < Z1, the sign change indicates a phase change of the reflected wave.

Applications of Sound in Medicine

Audiogram: a graph that shows the faintest sounds that can be heard (hearing threshold) and the loudest sounds that can be heard without pain (pain threshold).
Stethoscope: a diagnostic instrument that amplifies sounds made by the body from the heart, lungs, or other body sites.

Sonic Spectrum

The human ear can hear sounds in the range of roughly 20 Hz to 20 KHz.
Infrasound: refers to sound frequencies below the normal hearing range or less than 20Hz.
Ultrasound: is the frequency range above 20KHz.

Infrasound

Infrasound can travel long distances without losing much power due to its low absorption and large wavelength.
Infrasound can produce clear symptoms including respiratory impairment, aural pain, fear, visual hallucinations, and chills.
Infrasound can be used in the study of heart mechanical function.

Ultrasound

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 characteristics of sound waves, reflection and transmission, intensity level ratio, and applications of sound in medicine, including percussion and stethoscope.