Sound 2 Flashcards
Sound can be described in terms of _________—from the low rumble of distant thunder to the high-pitched buzzing of a mosquito—and __________.
Pitch and loudness
Technically, sound is defined as
a mechanical disturbance traveling through an elastic medium—a material that tends to return to its original condition after being deformed. The medium need not be air; metal, wood, stone, glass, water, and many other substances conduct sound, many of them better than air.
Objective, measurable qualities of sound include _______ and _______, which are related to pitch and loudness.
frequency and intensity, which are related to pitch and loudness.
A vibrating object will produce sound waves in the air. For example, when the head of a drum is hit with a mallet, the drumhead vibrates and produces sound waves. The vibrating drumhead produces sound waves because it moves alternately outward and inward, pushing against, then moving away from, the air next to it.
air molecules that strike the drumhead while it is moving outward rebound from it with more than their normal energy and speed, having received a push from the drumhead. These faster-moving molecules move into the surrounding air. For a moment, therefore, the region next to the drumhead has a greater than normal concentration of air molecules—it becomes a region of compression
As the faster-moving molecules overtake the air molecules in the surrounding air, they
collide with them and pass on their extra energy. The region of compression moves outward as the energy from the vibrating drumhead is transferred to groups of molecules farther and farther away.
What is rarefaction? ( use a drumhead as an example).
Air molecules that strike the drumhead while it is moving inward rebound from it with less than their normal energy and speed. For a moment, therefore, the region next to the drumhead has fewer air molecules than normal—it becomes a region of rarefaction. Molecules colliding with these slower-moving molecules also rebound with less speed than normal, and the region of rarefaction travels outward.
What is one cycle?
Each compression and the following rarefaction makes up one cycle. (A cycle can also be measured from any point on the curve to the next corresponding point.)
Define Frequency of a sound.
The ___________ of a sound is measured in cycles per second, or hertz (abbreviated Hz).
Define Amplitude of a sound.
The____________ is the greatest amount by which the concentration of air molecules varies from the normal.
What is the wavelength of a sound?
The ___________ of a sound is the distance the disturbance travels during one cycle. It is related to the sound’s speed and frequency by the formula speed/frequency = wavelength. This means that high-frequency sounds have short wavelengths and low-frequency sounds long wavelengths.
Intensity refers to
__________refers to the amount of energy transmitted by the disturbance. It is proportional to the square of the amplitude. Intensity is measured in watts per square centimeter or in decibels (db).
Pitch depends on the ______; in general, a rise in ________ causes a sensation of rising pitch.
_______ depends on the frequency; in general, a rise in frequency causes a sensation of rising ________.
In general, an increase in intensity will cause a sensation of __________ loudness.
In general, an increase in ________ will cause a sensation of increased loudness.
speed/frequency =
wavelength
We measure how loud sounds are in the form of
decibels (dB).
