Acoustics and Sound Waves

Noise is defined as unwanted energy from sources other than the transmitter.

Intermodulation results from interference of different frequencies sharing the same medium.

 Sound Wave's speed in the air is 330 m/sec

At resonance, the frequency of the external source becomes equal to the natural frequency of the object and the amplitude of the vibration becomes very large nearly infinite which is responsible for the breaking of the glass. 

Bats can hear frequencies up to 200 kHz, which is much higher than dogs (up to 45 kHz), humans (up to 20 kHz), and whales (most below 100 kHz, though some dolphin species hear ultrasound). This echolocation ability is crucial for their navigation.

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Sound travels fastest in solids because their particles are closely packed, allowing faster vibration transmission. Steel, being a solid with high elasticity, transmits sound much faster (~5000 m/s) than liquids or gases. Water and alcohol are liquids where sound travels slower.

85 dB is typically cited as the maximum safe exposure limit for occupational hearing safety (about 8 hours exposure). Beyond this level, prolonged exposure can cause permanent hearing damage. The pain threshold is much higher (~120 dB), but 85 dB is the safety cutoff.

It is a characteric of a musical sound by which a loud sound can be distinguished from a faint sound.

It is the collection of reflected sounds from the surfaces, like in an auditorium.

This is the correct answer. It is a decrease in magnitude of current, voltage, power of signals in transmission between points.

A microphone converts sound waves (mechanical energy) into electrical signals (electrical energy) through a diaphragm that vibrates in response to sound pressure. This is the principle behind all audio recording and communication devices.

Sound travels fastest in solids (steel) because particles are closely packed and can transmit vibrations more efficiently than in liquids (water) or gases (hydrogen). Sound cannot travel in empty space (vacuum) as it requires a medium for propagation.

Traditional telephone lines (POTS) carry analog voice signals. The sound waves are converted to continuous electrical signals that vary in amplitude and frequency. Digital telephony came later with technologies like ISDN and VoIP. Note option A contains a typo.

Mach number is the ratio of an object's speed to the speed of sound in the surrounding medium. It is primarily used in aerodynamics to characterize aircraft speeds, especially at high velocities where compressibility effects become significant. Subsonic (<1), transonic (~1), and supersonic (>1) regimes are critical in aircraft design.