Introduction
Summary
- Sound, a type of longitudinal wave observable in liquids and gases, has a perceptible range for the human ear from 16 Hz to 20 kHz. Its basic physical characteristics include frequency, sound velocity, wavelength, and acoustic impedance, each playing a crucial role in sound's behavior and its interaction with environments. Sound intensity measures the energy flow per unit area, while phenomena like diffraction and interference account for sound's propagation changes and the superposition of waves, respectively. Extracorporeal shock wave lithotripsy exemplifies a practical application, utilizing sound's physical properties to non-invasively treat kidney and gallbladder stones through focused acoustic pulses.
- General Sound Characteristics:
- Longitudinal waves capable of propagating through liquids and gases.
- Audible range for humans is between 16 Hz and 20 kHz.
- Transverse wave is a wave that oscillates perpendicularly to the direction of the wave's advance. In contrast, a longitudinal wave travels in the direction of its oscillations
- Basic Physical Characteristics:
- Frequency (f): Determined by 1/T, where T is the period.
- Sound Velocity (v or c): The speed of sound, with (v =lambda times f). Velocity is higher in solids than in liquids, and lowest in gases.
- Wavelength (λ): Given by \(v/f\), it describes the spatial period of the sound wave.
- Acoustic Impedance (Z): Calculated as \(p \times v\), where p is the medium's density, representing resistance to sound wave propagation.
- Sound Intensity:
- The formula for sound intensity is: I = E/(A*t). Seeing as E/t is the same as the power (P), we can simplify this formula into I = P/A. , measuring the energy flow per unit area over time.
- Sound Wave Phenomena:
- Diffraction: The change in direction of sound wave propagation, bending around obstacles and spreading beyond openings.
- Interference: The combination of two or more waves in the same medium, leading to:
- Constructive Interference: Amplitudes add up, leading to "live spots" where the phase difference is a multiple of $2π$.
- Destructive Interference: Waves out of phase (180° or $π$ radians) cancel each other, leading to "dead spots.
- Noise protection
- Noise above 70 dB over a prolonged period of time may start to damage your hearing. Loud noise above 120 dB can cause immediate harm to your ears.
- The most common types of hearing protection devices include earplugs, earmuffs, and specially made devices. These devices provide an air-tight seal in the ear canal. They are generally cheap, effective, and easy to use.
- Applications in Medicine: