Physics
Sound is a longitudinal wave, meaning the displacement of the medium is parallel to the movement of the wave. Sound waves consist of alternating compressions and rarefactions and are unable to travel through a vacuum. The speed of sound depends on the medium it's passing through, and its calculation involves the equation V = √(B/ρ), where V represents the speed of sound, B represents the bulk modulus, and ρ represents the density of the medium. Sound travels the fastest through solids and slowest through gases.
The intensity of a sound wave is the average rate of energy transferred by the wave per square meter. The volume of a sound is subjective, based on the perceiver's anatomy and brain function, while the pitch of a sound is based on frequency. For humans, pitches from about 20 to 20,000 hertz are audible, and frequencies over 20,000 hertz are considered ultrasound. Ultrasound can be used in machines to compare the density of tissues and to determine blood flow in the body.
Lesson Outline
<ul> <li>Sound is a longitudinal wave</li> <li>Movement of particles is parallel to the movement of the wave</li> <li>Sound is based on mechanical vibration of the medium it's passing through</li> <li>No sound in a vacuum, where there are no particles</li> <li>Anatomy of a sound wave: <ul> <li>Compressions and rarefactions</li> <li>Compressed areas called compressions</li> <li>Spread out regions called rarefactions</li> </ul> </li> <li>Speed of sound equation: V = √(B / ρ)</li> <li>Factors affecting speed of sound: <ul> <li>Bulk modulus (B) - material's resistance to compression</li> <li>Density of the medium (ρ)</li> <li>Medium type - solids, liquids, or gases</li> </ul> </li> <li>Sound travels fastest through solids, slowest through gases</li> <li>Intensity of sound: average rate of energy transferred per square meter</li> <li>Volume (loudness) is subjective</li> <li>Pitch of sound based on frequency</li> <li>Human audible frequency range: 20 hertz to 20,000 hertz (20 kHz)</li> <li>Infrasonic and ultrasonic waves: <ul> <li>Infrasonic waves - below 20 Hz</li> <li>Ultrasonic waves - above 20,000 Hz</li> <li>Different species have different perceivable ranges</li> </ul> </li> <li>Ultrasound applications: <ul> <li>Comparing relative density of tissues (sonography)</li> <li>Therapeutic applications, e.g., breaking up kidney stones</li> <li>Doppler ultrasound imaging - visualizing blood flow in the body</li> </ul> </li> </ul>
Don't stop here!
Get access to 29 more Physics lessons & 8 more full MCAT courses with one subscription!
FAQs
Properties of sound include pitch, volume, intensity, and speed. Pitch refers to the perception of how high or low a sound is and is related to its frequency, which is the number of cycles per second (measured in hertz). Volume is the loudness of a sound, which is influenced by its amplitude, while intensity, or power per unit area, is measured in decibels (dB). The speed of sound depends on the medium it travels through, with sound traveling faster in solids and liquids compared to gases.
In a longitudinal wave, particles of the medium move parallel to the direction of the wave, creating areas of high (compressions) and low (rarefactions) particle density or pressure. Sound waves are longitudinal waves, and as the wave travels through a medium, the compressions and rarefactions cause fluctuations in the air pressure, creating the mechanical vibrations we perceive as sound.
The speed of sound depends on the properties of the medium it travels through, such as its density and elasticity. For instance, sound travels faster in solids and liquids compared to gases because their particles are closer together, allowing vibrations to be transmitted more efficiently. Additionally, temperature can influence the speed of sound, with higher temperatures leading to faster sound propagation as particles have increased kinetic energy and move more rapidly.
An ultrasound is a diagnostic imaging technique that uses high-frequency sound waves to create images of internal body structures. In medicine, ultrasound is commonly used for examining soft tissues like muscles, tendons, and internal organs to diagnose various conditions, monitor fetal development, and guide certain medical procedures. The technique is non-invasive and involves transmitting sound waves through a patient's body using a transducer, which sends and receives signals to create images based on the reflection and absorption of sound waves by different tissues.
Doppler ultrasound is a specialized type of ultrasound that measures the frequency shift of reflected sound waves to assess the movement of blood or other fluids within the body. This technique is based on the Doppler effect, in which the frequency of a wave changes relative to the observer when the source of the wave is moving. In medical practice, Doppler ultrasound is often used to evaluate blood flow in vessels, detect blood clots, and monitor fetal blood flow during pregnancy. It can also help diagnose and monitor certain cardiovascular conditions such as arterial blockages and valve defects.
