>>21266117let me answer in more detail. first, it is a water heater, absolutely and factually, and there is no reason to doubt it. she is in the room, knows where the water heater is, can look at it, and can hear it with both ears when it goes on and off. second, it does come and go. there are times when she talks with no music and the sound does not make it into the stream. when her noise gate closes, it disappears completely. so, it is something in the signal coming out of the mic preamp. it is not electrical hum, because it is not the AC frequency used anywhere in the world. by far the most realistic explanation of the evidence is that it is exactly as she said: it is the water heater.
as for why it started to become obvious, it's most likely because she rearranged her setup slightly. a slight change can affect things like this in unexpected ways. for example, a five-degree change in the orientation of my shock mount drastically increases how much of the mic stand resonance makes it through to the mic. not like 2 dB... it's like 20 dB. the frequency of the water heater is one that causes standing waves all over a typical residential room in a sparse checkerboard of loud spots and
quiet spots. if you've tried to set up a single-subwoofer system in a rectangular room you've surely run into this. moving her mic stand from one side of the desk to the other could easily be enough to have caused the change.
