Produced by reflected sound waves over 17m away?
You are too close to the surface from which the sound waves are reflected. As a result you brain cannot distinguish between the original sound waves and the reflexted sound waves (the echo).
The source that emitted the sound wave.
The Doppler Effect describes a frequency shift in reflected waves in proportion to the relative speed between the receiver and the reflected object. For instance, in a radar speed trap, the frequency shift in reflected radio waves allows the unit to calculate the speed toward (higher frequency) or away from (lower frequency) the transmitter/receiver unit. When you drive past a steady noise source, such a bell or a horn, the sound has a higher frequency as you approach and a lower frequency as you depart.
Sound waves move away from the source of energy, but other sorts of waves move perpendicular (at a right angle) to the energy source
The siren moves away from the sound waves it has already produced, increasing their wavelength. Make sure it says INCREASING and not DECREASING -Apex :)
They get distant and more quieter
far away
farther away
This is an example of the Doppler effect. Sound is composed of waves. A particular vibration produces a sound wave with a particular wavelength. When the sound source moves towards a listener the waves are "bunched up". That results in a shorter observed wavelength and thus a higher frequency. When the sound source moves away the opposite happens. The frequency of the sound waves decreases.
This is an example of the Doppler effect. Sound is composed of waves. A particular vibration produces a sound wave with a particular wavelength. When the sound source moves towards a listener the waves are "bunched up". That results in a shorter observed wavelength and thus a higher frequency. When the sound source moves away the opposite happens. The frequency of the sound waves decreases.
they funnel in the sound waves from the enviroment
There energy decreases