2.5 Wave Motion and Sound (Lvl 2) Flashcards
What is a mechanical wave?
An oscillation of matter.
What are types of mechanical waves?
Sound waves
Slinky Waves
Water Waves.
What does a mechanical wave require to transmit energy?
A medium.
What type of medium does sound waves require?
Air molecules.
What type of medium does Slinky wave require?
A slinky.
What type of medium does ocean waves require?
Water.
Where can’t mechanical waves exist?
In a vacuum.
What can mechanical waves be classified as?
Transverse or longitudinal, depending on how they travel.
What is a transverse wave?
Where it causes the medium to vibrate at a 90 degree angle to the direction of the wave.
What is the highest point of the wave called?
Crest
What is the lowest point of the wave called?
Trough
What is a longitudinal wave?
Displacement of the medium that is parallel to the propagation of the wave.
What is it called when the particles travelling through a wave are close to together?
Compression.
What is it called when the particles travelling through a wave are spread apart?
Rarefaction (Expansion).
What is an example of longitudinal waves?
Sound Waves.
What is an example of a transverse waves?
Water waves.
What are the characteristics of a sine wave?
Repeats itself at stand intervals with a constant amplitude.
What is amplitude?
Is the greatest displacement from the rest point.
What is wavelength?
Is the distance from one point on the wave pattern to the next point in a similar position (Peak to Peak).
What is periodic time?
The time taken to complete 1 oscillation.
what is frequency?
The number of complete oscillations in one second.
What is wave interference phenomena?
Where two waves meet whilst travelling along the same medium and form a wave of greater, lower or the same amplitude.
It causes the medium to take on a shape the results from the net effect of two individual waves.
What is a standing wave also known as?
A stationary wave.
What is the wider definition of sound?
Sounds that include low and high frequency vibrations in air that cannot be heard by humans, and vibrations that travel through all forms of matter (Gas, Liquid and Solids).
What does the speed of which sound waves travel at depend on?
The medium that the waves pass through.
What is the speed of sound, when air is at room temperature?
Approx. 343m/s.
What is the speed of sound, when in water?
Approx. 1500m/s.
What is the speed of sound, when through a bar of steel?
Approx. 5000m/s
Why is it important to consider the speed of sound in terms of the aerodynamics of an aircraft?
Because it is the point at which the air becomes increasingly compressible and the flying characteristics change drastically.
What is the equation for the speed of sound?
c = 20 x SqRoot of T
c = Speed of sound in air (m/s) T = Temperature (Kelvin).
What is Mach Number?
It describes the ratio of the speed of an aircraft in relation to the speed of sound.
What is the equation for Mach number?
M = v/c
M = Mach number v = speed of object (m/s) c = speed of sound(m/s).
How is sound produced?
It is normally a result of a mechanical disturbance on an object causing it to vibrate.
What does the loudness of sound depend on?
The amplitude of the vibrations and the distance from the source.
Where can sound not be transmitted?
Through a vacuum.
How are sound waves propagated?
Longitudinal Waves.
What will air have as a result of its density?
Low density = Rarefaction
High density = Compression.
In sound, what is the result of a higher amplitude?
Louder sound.
At what decibel can cause permanent damage to a persons hearing?
85dB.
At what decibel can cause serious pain and permanent damage to a persons hearing?
130dB.
What does pitch of a sound depend on?
The frequency of sound
ie. higher frequency, higher pitch and vice versa.
What characteristic of sound enables humans to distinguish between the voices of men and women?
The pitch.
What is pitch of a tone proportional to?
The number of compressions and rarefactions received per second, which is determined by the vibration frequency of the sound source.
The property of sound, Quality, is used to do what?
To distinguish between 2 sounds of the same pitch and loudness, ie, sounds originating from 2 different musical instruments.
What is tone of the lowest frequency called?
Fundamental frequency.
When a fundamental frequency is determined, what are the other tones known as?
Overtones or harmonics.
What are the 3 characteristics of sound?
- Loudness
- Pitch
- Quality.
What is the doppler effect?
Describes the change of frequency of a wave caused by the movement of a body relative to the wave source.
In simpler terms, what is the doppler effect?
The ear hears a higher frequency as the source and observer approach each other,
The ear hears a lower frequency when the source and observer recede from each other.
When may the doppler effect be used in aircraft systems?
Detecting weather by measuring the motion of rain droplets and intensity of precipitation.
