Detecting whether a sound has become farther away or has simply become quieter without a change in position can be challenging. However, there are certain cues and techniques you can use to make an educated guess. Here are a few ways to approach this:
Intensity: As sound waves propagate through space, their intensity decreases with distance. If you observe a decrease in the intensity or volume of the sound, it could indicate that the sound source has moved farther away. However, keep in mind that other factors, such as obstacles or environmental conditions, can also affect sound intensity.
Doppler effect: The Doppler effect describes the change in frequency of a sound wave as the source or the listener moves relative to each other. If the frequency of the sound appears to be changing, it may suggest that the sound source is moving. For example, if the pitch appears to decrease, it could indicate that the source is moving away. However, this method requires comparing the observed sound to a known reference frequency.
Directional cues: If you can determine the direction from which the sound is coming, changes in its apparent position can provide clues. For instance, if the sound appears to be coming from a different direction but maintains the same volume, it could indicate that the source has not moved but has become quieter.
Environmental factors: Consider the environment in which the sound is occurring. Changes in the acoustics of the space, such as the presence of reflecting surfaces or ambient noise levels, can impact the perceived loudness and apparent position of a sound.
Contextual information: If you have additional information about the sound source or the situation, it can help you make an informed judgment. For example, if you know that the sound source is stationary and you observe a decrease in volume, it is more likely that the sound has become quieter rather than moved.
Remember that these methods are not foolproof and rely on various assumptions and observations. It's often best to combine multiple cues and use your judgment to make a reasonable inference about changes in sound distance and volume.