Reflection
Sound doesn’t just travel from the speakers to your ears, it radiates out in all directions. It bounces off the walls, ceiling, floor, and other solid objects in the room. These reflections can then, you guessed it, reflect off a surface for a second, third, fourth etc. time. Each reflection will lose a bit of power and they will eventually decay naturally. This pattern of reflections are what give a room a characteristic reverberant sound. Be mindful of this characteristic during your battle! The worst reflective offenders being surfaces within 3 metres of the listening position. Be mindful of the surfaces on your workstation. A solid flat surface like the top of a desk can cause serious reflections that lead to comb filtering – which we will touch on later.
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Flutter echo
High frequency reflections caused by sounds bouncing between two parallel surfaces. Check for this distinctive metallic buzz by clapping your hands and listening for the brief echo. This is one of the easiest problems to fix, so read on to find out more about the weapons at your disposal!
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Standing waves
Also known as room modes. More prominent in low frequencies, and with parallel surfaces, this phenomenon cause frequencies volumes to both increase and decrease in specific spots within the room. This is a complex physical process, and it has to do with the particular length of a frequency soundwave – this is, astonishingly enough, called wavelength.
The waves are comprised of high and low pressure areas, so when we combine these regular undulations of pressure with reflections, we can get big problems! Reflected waves layer up making the pressure difference between high and low even more pronounced.
The interaction between wavelength, and room dimensions means that these pressure zones appear at very specific spots in a room. Depending on where you are listening from, the frequency of the standing wave can be boosted or cut, so understanding where these points are is absolutely essential!
You want to listen from a point of neutral pressure, and you want to target these frequencies with acoustic treatment – more on this later.
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Resonance
The transfer of sound from one object to another. This can add an unwanted frequency boost. Be wary of anything directly connected to a speaker, and the things connected to that thing, and that thing etc. etc. Resonance takes time to dissipate, so sounds continue in what is knows as the ‘time domain’. This leads to frequencies ‘ringing out’ way after the speaker has stopped producing this frequency. This can really upset the balance of frequencies, as well as the ‘tightness’ of the sound.
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Comb filtering
When the same sound arrives at the listening position at different times, frequencies become out of phase, and can lead to comb filtering. The high and low parts of the sound interact destructively to change the sound. This is a simple physical effect that occurs at regular points along a frequency and can lead to the sound becoming less ‘full’, or even produce an unnatural sweeping resonance. This is actually used to produce effects in music production such as chorus and flanging.
