Acoustics and Sound Waves

Sound is a mechanical wave that requires a medium to propagate. Since a vacuum contains no particles to transmit the vibrations, sound cannot travel through it.

Ultrasound is defined by its frequency, which is above the range of human hearing (typically above 20,000 Hz). Audible sound falls within the 20 Hz to 20,000 Hz range.

Sound waves require a medium to travel. The speed of sound depends on the medium's elasticity and density; solids have much higher elastic moduli than liquids, which allows sound waves to propagate faster.

Sound waves exhibit reflection, refraction, interference, and diffraction. Polarization is a property unique to transverse waves, such as light, whereas sound waves are longitudinal and cannot be polarized.

Thunder is caused by the rapid expansion of air due to lightning. The sound reflects off various surfaces like clouds, mountains, and buildings, creating multiple echoes that result in the characteristic rumbling sound.

The human ear can detect sound intensities starting from 0 dB (the threshold of hearing) up to about 180 dB (which causes immediate damage). The other ranges listed are far beyond the threshold of pain.

Sound travels fastest in solids because the particles are more closely packed together, allowing for more efficient transmission of mechanical vibrations. Steel is a dense solid.

The decibel (dB) is a logarithmic unit used to measure the intensity or level of sound.

The outer ear is called the ‘pinna’. It collects the sound from the surroundings.

Hence, option 1 is correct.

Resonance occurs when an external periodic force is applied to a system at its natural frequency, causing it to vibrate with large amplitude. This is a specific case of forced vibrations.

Sound waves are mechanical waves that transport energy through a medium. They do not transport mass (particles only oscillate) and do not transport 'sound' itself - sound is the energy wave. The wave carries energy from source to receiver.

According to the World Health Organization and various environmental standards, noise levels above 80 dB are generally considered the threshold for potential hearing damage and hazardous noise pollution.

Sound is produced when an object vibrates, creating pressure waves in a medium like air. Light, wind, and water are distinct physical phenomena not primarily defined by vibration in this context.

The pinna (or auricle) is the visible part of the outer ear that collects sound waves and directs them into the ear canal.

The ear drum, or tympanic membrane, is a thin, cone-shaped membrane that separates the external ear from the middle ear. It vibrates in response to sound waves entering the ear canal.