ebr love wrote:Lorgar's explanation covered that?
'When you fire, the bullet leaves your barrel at super sonic speeds and because it's moving faster than the speed of sound it's outrunning it's own shockwave."
As per the picture?
I'd like to read the source page for the above diagram so as I can better understand. My experience relates to sound reinforcement and radio transmission, so my experience is in an entirely different area.
That isn't the Doppler effect as I understand it.
This is my understanding.
http://en.wikipedia.org/wiki/Doppler_effectThe Doppler effect (or Doppler shift), named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.
The relative changes in frequency can be best explained as follows. When the source of the waves is moving toward the observer, each successive wave crest is emitted from a position closer to the observer than the previous wave. Therefore each wave takes slightly less time to reach the observer than the previous wave. Therefore the time between the arrival of successive wave crests at the observer is reduced, causing an increase in the frequency. While they are travelling, the distance between successive wave fronts is reduced; so the waves "bunch together". Conversely, if the source of waves is moving away from the observer, each wave is emitted from a position farther from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. The distance between successive wave fronts is increased, so the waves "spread out".
For waves that propagate in a medium, such as sound waves, the velocity of the observer and of the source are relative to the medium in which the waves are transmitted. The total Doppler effect may therefore result from motion of the source, motion of the observer, or motion of the medium. Each of these effects is analyzed separately. For waves which do not require a medium, such as light or gravity in general relativity, only the relative difference in velocity between the observer and the source needs to be considered.
EDITFound this:
Source moving with vsource > vsound (Mach 1.4 - supersonic)
The sound source has now broken through the sound speed barrier, and is traveling at 1.4 times the speed of sound (Mach 1.4). Since the source is moving faster than the sound waves it creates, it actually leads the advancing wavefront. The sound source will pass by a stationary observer before the observer actually hears the sound it creates.
As you watch the animation, notice the clear formation of the Mach cone, the angle of which depends on the ratio of source speed to sound speed. It is this intense pressure front on the Mach cone that causes the shock wave known as a sonic boom as a supersonic aircraft passes overhead. The shock wave advances at the speed of sound v, and since it is built up from all of the combined wave fronts, the sound heard by an observer will be quite intense. A supersonic aircraft usually produces two sonic booms, one from the aircraft's nose and the other from its tail, resulting in a double thump. The figure at right shows a bullet travelling at Mach 2.45. The mach cone and shock wavefronts are very noticeable.
I've got it now, always something new to learn
