Please, pardon my ignorance. This may be a simple question, but I am still unable to explain what is happening.
I am using a turtlebot to listen to sound emitted from a stationary sound source.
My experiment setup is this:
- One stationary sound source emits tone of 500Hz.
- A turtlebot robot located about 3.5m away listens and measures the amplitude of the sound source (used FFT and filtered out 500Hz) at a rate of 100Hz while moving linearly toward the sound source at a velocity of 0.1m/s.
The result of the measurements is shown below. NB: X axis is distance in metres, Y axis is amplitude measured by the turtlebot.
My question is this: 1. Why is there a noticeable dip in the amplitude as the robot moves closer to the sound source? 2. Please can you help me with links to resources that can help me explain this behaviour?