Sound
Sound is a vital form of energy manifested through the vibrations of objects. These vibrations generate longitudinal waves that propagate through different media—solids, liquids, and gases—indicating sound's dependency on the medium itself. Notably, sound cannot travel through a vacuum because it relies on particle interaction for transmission.
Characteristics of Sound Waves
Sound waves exhibit various characteristics including:
1. Wavelength (λ): The distance between successive compressions or rarefactions.
2. Frequency (f): The number of vibrations per second, measured in Hertz (Hz).
3. Amplitude (A): The maximum displacement of particles from their rest position.
4. Time Period (T): The time needed to complete one full vibration, expressed mathematically as T = 1/f.
5. Speed (v): Determined by the medium and its temperature, calculated by the formula v = f × λ.
Types of Sound
Sounds are categorized into:
- Audible Sounds: Ranging from 20 Hz to 20,000 Hz, detectable by humans.
- Infrasonic Sounds: Below 20 Hz, such as those produced by earthquakes.
- Ultrasonic Sounds: Above 20,000 Hz, utilized by animals like bats and even in medical applications.
Reflection of Sound
Sound reflects according to similar principles as light:
- The angle of incidence equals the angle of reflection.
- An echo occurs when reflected sounds are heard after a time lag of at least 0.1 seconds. For an echo to be heard, it needs to travel a minimum distance of 17.2 m.
- Reverberation results from multiple reflections of sound.
Practical Applications
Reflection of sound is utilized in various applications like megaphones, soundboards, stethoscopes, and technologies like SONAR and echo depth sounding.
Hearing Range
Humans can typically hear within a frequency range of 20 Hz to 20,000 Hz, which diminishes with age. Animals extend this range, with species such as dogs and bats able to hear ultrasonic frequencies.
The Human Ear
The ear converts sound waves into electrical signals for interpretation by the brain, encompassing various structures such as the outer ear, ear canal, eardrum, middle ear bones (ossicles), cochlea, and auditory nerve.