Properties and Types of Sound Waves Quiz

Properties of Sound Waves

Sound waves are longitudinal pressure waves caused by vibrating particles. They propagate through various media such as air, water, and solids. Let's examine some key properties:

• Speed: The speed of sound depends on the medium through which it travels. In dry air at room temperature, sound travels approximately at 343 meters per second (m/s) or 1,125 feet per second. This value increases with rising temperature due to the expansion of air molecules. For instance, at 20°C (68°F), it is around 334 m/s (1,095 ft/sec). In water, sound travels at around 1,500 m/s (4,921 ft/sec), and in steel, it reaches approximately 5,960 m/s (19,553 ft/sec).

• Wavelengths: Sound waves vary in wavelength, ranging from less than 1 cm to several meters. Longitudinal sound waves cause compression and expansion cycles as they propagate through a medium. The frequency determines the size of the wave, which is inversely proportional to wavelength. As examples:

  • Higher frequencies produce shorter wavelengths and higher pitches; e.g., ultrasonic waves produced by dolphins have wavelengths between 0.2 and 30 meters.
  • Lower frequencies generate longer wavelengths and lower pitches, such as those emitted by large whales that range from 10 to 100 km.

• Amplitude: The amplitude of a sound wave measures the intensity or loudness of a vibration. Greater amplitudes represent stronger waves leading to increased volume.

Types of Sound Waves

There are three main categories of sound waves based on their frequency: audible, infrasound, and ultrasound.

Audible Sound Waves

Audible sounds fall within the human hearing range, typically between 20 Hz and 20,000 Hz. These sounds have wavelengths ranging from 0.001 mm to 17 m. Examples include speech, music, and environmental noise.

Infrasound

Infrasound refers to low-frequency sound waves that are below the audible limit of humans. They can travel far distances due to their long wavelengths, enabling animals such as elephants and whales to communicate across great distances. Infrasound can occur naturally, like volcanic eruptions, earthquakes, and tornadoes, or manmade like explosions and sonic booms.

Ultrasound

Ultrasound refers to high-frequency sound waves above the upper limit of human hearing. Humans cannot hear these sounds, but they have numerous practical applications, including medical imaging, noninvasive procedures, and industrial inspections. Commonly used frequencies are in the range of 20 kHz to 200 MHz, mostly for medical purposes. However, they can extend beyond the frequency range of 10 GHz, suitable for industrial applications.