Ultrasound Physics Ch. 2 - 6

Sound waves carry energy because they are mechanical waves that transfer energy through the vibration of particles in a medium. As sound waves propagate, they cause the particles in the medium to oscillate back and forth, transferring energy from one particle to the next. This energy transfer allows sound waves to travel through different mediums, such as air, water, or solids. Therefore, it is true that sound waves carry energy.

Diffuse reflection or back scattering occurs when a wave reflects off an irregular surface, causing it to radiate in more than one direction. This is because the interfaces in the body are not smooth and have some irregularities. Therefore, the given statement is true.

Sound waves are indeed longitudinal waves, meaning that the particles in the medium through which sound travels vibrate parallel to the direction of the wave. This is in contrast to transverse waves, where the particles vibrate perpendicular to the direction of the wave. Additionally, sound waves generally travel in a straight line, as long as there are no obstacles or changes in the medium that cause the wave to bend or reflect. Therefore, the statement "sound travels in a straight line" is true.

The given answer lists various acoustic parameters, including period, frequency, amplitude, power, intensity, wavelength, and propagation speed. These parameters are used to describe different aspects of sound waves. The period refers to the time it takes for one complete cycle of a wave, frequency is the number of cycles per second, amplitude represents the maximum displacement of particles in a wave, power is the rate at which energy is transferred by the wave, intensity is the amount of energy carried by the wave per unit area, wavelength is the distance between two consecutive points in a wave, and propagation speed is the rate at which the wave travels through a medium.

Short wavelength sound produces higher quality images with greater detail because shorter wavelengths have higher frequencies. Higher frequencies allow for more precise imaging and capturing of smaller details. Therefore, short wavelength sound is able to produce clearer and more detailed images compared to long wavelength sound.

the correct answer to this will be in phase NOT out of phase

As frequency increases, the number of complete waves passing a point per unit time increases. Since the speed of a wave is constant, increasing the frequency means that the waves must be closer together in order to pass the same point in the same amount of time. Therefore, as frequency increases, the wavelength, which is the distance between two consecutive points in a wave, must decrease.

The acoustic variables refer to the physical properties that characterize sound waves. Pressure is a measure of the force exerted by the sound wave on a surface, density is the mass of air molecules in a given volume, and distance refers to the spatial displacement of the sound wave. These variables are essential in understanding the behavior and characteristics of sound waves.

Bioeffects refers to the effects of sound waves on tissue in the body. When sound waves interact with biological tissues, they can cause various physiological changes and potential damage. These effects can include thermal (heating) and non-thermal (mechanical) effects, such as tissue heating, cavitation, and acoustic streaming. Understanding and studying these bioeffects is crucial in the field of medical ultrasound and other applications that involve the use of sound waves in the body.

The period and frequency of a sound wave are determined by the characteristics of the sound source. The sound source, such as a musical instrument or a person's voice, produces vibrations that create the sound wave. The frequency of the sound wave is determined by the rate at which these vibrations occur, while the period is the time it takes for one complete vibration cycle. Therefore, the sound source plays a crucial role in determining the period and frequency of a sound wave.

Deeper imaging refers to the process of capturing more detailed or extensive information about a particular subject or object. In the context of listening, deeper imaging would involve being able to perceive and understand more nuances, subtleties, or layers in the audio. Therefore, it is logical to assume that with deeper imaging, the listening time would lengthen as it would take more time to fully comprehend and process the additional information. Hence, the correct answer is "yes".

Normal incidence refers to the situation when a ray of light or any other wave approaches a surface at a right angle or 90 degrees. In this context, "perpendicular," "orthogonal," "right angle," and "90 degrees" all describe the same concept of normal incidence.

all three ARE adjustable

Shallow imaging on PRP refers to the use of a shorter pulse repetition period (PRP). PRP is the time interval between consecutive pulses in an imaging system. By using a shorter PRP, the imaging system can acquire images at a faster rate, allowing for a higher temporal resolution. This means that more images can be captured within a given time frame, resulting in a more detailed and accurate representation of the shallow structures being imaged. Therefore, the correct answer is a shorter PRP.

The spatial pulse length definition refers to the distance that a pulse occupies in space from its start to its end. This means that it measures the physical length of the pulse as it travels through space. It does not refer to the time it takes for the pulse to travel or the frequency of the pulses being transmitted.

The duty factor is defined as the fraction of time that an ultrasound system is transmitting a pulse. When imaging depth is altered, the sonographer needs to adjust the duty factor to maintain optimal image quality. This is because as the depth increases, the ultrasound pulse needs more time to travel to and from the target, so the duty factor needs to be decreased to allow for longer listening time. Conversely, when imaging depth is decreased, the duty factor needs to be increased to maintain adequate penetration and resolution. Therefore, it is true that the sonographer changes the duty factor when imaging depth is altered.

Infrasound refers to sound waves that have a frequency below the range of human hearing, which is typically between 20 Hz and 20 kHz. Therefore, the correct answer is "between 20 Hz & 20 kHz". The answer ">20 kHz" is incorrect as it suggests a frequency above the range of human hearing.

remember , power is related to the intensity (pg.31)
so if power is tripled the intensity is tripled as well

When the boundary is smooth, the sound waves bounce off the surface in a predictable and organized manner, reflecting in only one direction. This phenomenon is known as specular reflection. Unlike diffuse reflection, where the waves scatter in various directions, specular reflection results in a clear and focused reflection.

The amplitude, power, and intensity of a sound are determined by the sound source. The sound source is responsible for producing the vibrations that create the sound waves. The amplitude refers to the maximum displacement of the particles in the medium caused by the sound waves. The power is the rate at which energy is transferred by the sound waves. The intensity is the power per unit area and determines the loudness of the sound. Therefore, the characteristics of the sound source directly influence these properties of the sound.

The propagation speed of sound is determined by the medium through which it travels. Different mediums, such as air, water, or solids, have different densities and elastic properties, which affect the speed at which sound waves can travel through them. The speed of sound is generally faster in denser mediums, such as solids, and slower in less dense mediums, such as gases. Therefore, the medium plays a crucial role in determining the propagation speed of sound.

The wavelength of a sound wave is determined by both the sound source and the medium through which it travels. The sound source, such as a musical instrument or a speaker, produces the sound wave with a specific frequency. The medium, which can be air, water, or any other substance, affects the speed at which the sound wave travels. The wavelength is directly related to the frequency and the speed of the wave. Therefore, both the sound source and the medium play a role in determining the wavelength of a sound wave.

The pulse repetition period (PRP) refers to the time interval between consecutive pulses in a radar system. It determines the maximum range at which the radar can detect targets. The PRP can be adjusted based on the specific requirements of the radar system. By adjusting the PRP, the radar can optimize its performance for different operating conditions, such as target range, clutter conditions, and desired resolution. Therefore, the answer "yes" indicates that the PRP is adjustable in order to meet the needs of the radar system.

When the sonographer adjusts the depth of view to 30 cm, the pulse repetition frequency is reduced. This is because as the depth of view increases, the ultrasound waves have to travel a longer distance before returning to the transducer. To maintain image quality, the pulse repetition frequency needs to be reduced so that the ultrasound waves have enough time to travel to the desired depth and back before the next pulse is emitted. This allows for accurate imaging and better visualization of structures at greater depths.

The meaning of 3dB is that the signal or power level has doubled. In terms of decibels, a 3dB increase represents a doubling of the original value. This can be applied to various contexts, such as audio systems or electrical circuits, where a 3dB increase indicates a doubling of the signal strength or power.

The statement "PRF and frequency are related" is false. PRF (Pulse Repetition Frequency) is a measure of the number of pulses emitted per second, while frequency refers to the number of cycles per second in a waveform. Although both terms are related to the concept of time, they are not directly related to each other. PRF is typically used in radar systems to determine the rate at which pulses are transmitted, while frequency is a more general term used in various fields to describe the rate of oscillation or vibration.

The start of a pulse to the end of that pulse refers to the duration of the pulse, which is the time it takes for the pulse to occur. This is different from the spatial pulse length, which refers to the length of the pulse in space. The pulse repetition period and pulse repetition frequency are related to the time between consecutive pulses, not the duration of a single pulse. Therefore, the correct answer is pulse duration.

the correct answer is C because the question asks for the longest PRP
since PRF and PRP are reciprocals you will have to look for the lowest PRF

The duty factor is a measure of the fraction of time that a pulse is on or active compared to the total pulse repetition period (PRP). It is calculated by dividing the pulse duration by the PRP and then multiplying by 100 to express it as a percentage. Therefore, the correct formula for calculating the duty factor is pulse duration / PRP x 100.

intensity of sound to ONE-HALF it original value

when PRP increases , depth of view increases

The path length refers to the distance that the ultrasound waves travel through soft tissue. As the path length decreases, it means that the waves have to travel a shorter distance. This shorter distance results in less interaction with the soft tissue, leading to a decrease in attenuation. Attenuation refers to the weakening or loss of intensity of the ultrasound waves as they pass through the tissue. Therefore, as the path length decreases, the attenuation of ultrasound in soft tissue also decreases.

pulse duration is INVERSELY proportional to the frequency
recall that pulse duration formula is # cycles / frequency
pg. 48

The amplitude of a wave refers to the maximum displacement or distance from the equilibrium position of a particle in the wave. In the context of acoustic variables, such as sound waves, the amplitude represents the maximum pressure variation or displacement of air particles caused by the sound wave. Therefore, the units for amplitude in this case would be related to the specific acoustic variable being measured, such as pascals (Pa) for pressure or meters (m) for displacement.

describes the MAXIMUM distance

The half value layer thickness refers to the amount of material required to reduce the intensity of a sound wave to half its original value. This parameter depends on both the frequency of sound and the medium through which it propagates. The frequency of sound affects the attenuation of the wave, while the medium determines the density and properties of the material that the sound wave encounters. Therefore, both factors play a role in determining the half value layer thickness.

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10 x 10 = 100

Water has high attenuation for many types of electromagnetic waves, especially radio and microwave signals, meaning these signals lose strength quickly as they pass through water. This is why underwater communication often relies on sound waves (sonar), which travel better in water. High attenuation limits the effectiveness of wireless signals like GPS or Wi-Fi underwater.

The pulse duration is defined as the time it takes for one pulse to complete. It is measured in seconds. The formula for pulse duration is the number of cycles divided by the frequency. This formula calculates the duration of a pulse by dividing the number of cycles in the pulse by the frequency at which the pulse occurs.

Period and frequency are inversely related to each other. This means that as the period increases, the frequency decreases, and vice versa. This relationship can be represented mathematically as f = 1/T, where f is the frequency and T is the period. The term "reciprocal" is often used to describe this inverse relationship, as the frequency is the reciprocal of the period. Therefore, the correct answer is "inversely, reciprocal."

Gain settings control the amplification of the returning echoes, influencing the brightness of the image. While improper gain can obscure details, it doesn't fundamentally alter the resolution. Resolution is primarily determined by the transducer frequency (higher frequency, better resolution), pulse repetition frequency (limits the depth of imaging), and the acoustic impedance of the tissues (mismatches create reflections that define boundaries).