Its funny really, the answer apparently, is Gryllidae.
Its funny really, there are so many noises heard in the dead of the night. You wonder what they are and where they come from. The one that is hardest to hear of all is the tick of the clock. The tick is buried in the subconscious as a very common sound, so it takes particular effort to hear. But its always there, and most households have more than one timepiece. That means there is more than one tick, clocks don't all tick together, no matter how close to time they are. So there is a loud set of ticks close by, and a whole bunch of fainter sets of ticks from all around - its a fraction of the ambient noise of the night.
Water dripping. Pretty picturesque, but leaky taps are only half the problem. That too, is a common sound, but the problem is there are a whole bunch of sounds not from faucets, but of water dripping nonetheless. The Air Conditioners of a standard housing society have a light metal din going on almost all the time. A drop of water from the twelfth floor may encounter a lot of aluminium sheeting before it ends up in the skies the next morning. Piping's are peppered with small bursts of drain water escaping into a slight splash of a pool below. And abandoned vehicles leaking fluids make a soft "splichfsss" of a sound. Ends up as muck and grease.
Many other things go on in the night now a days. Television programs, the radio, some guy with a good stack of pirated Cd's... you never know what faint echo will die just short of your ears. In certain conditions, some guy with a good audio setup in his car blasting psytrance can be heard faintly but distinctly from kilometers away because of the kind of music trance is.
Vehicles... alarms going off as somebody brushes past, in reverse and sounding recently out dated songs in jarring tones, and worst of all, honking. There will be late night bikers racing by, the odd party in a car that could support a village, and of course, the good police on their periodic patrols. When an ambulance goes by in the middle of the night... you might just wake up with a bad dream.
Doors. Opening, closing. Keys. Jingling. Footsteps, going up and going down and round about. What is imagined, what is real, what is mistaken, is anybodies prerogative. The elevators, have an alarm for when their doors are open. More or less, the sound is "Krrrr...." There are many elevators around, so it is very likely that there is a faint "krrr..." somewhere about always. The "Krrrrr...." is the one sound that can really freak the living hell out of someone.
Imagine, spending sleepless nights wondering why in hell there is a faint "krrrr" always about in the night? It is pretty easy to hear. Just stick your head into a night, and the sound will come right into your ears. It is distinct, unwavering and constant. Where the hell must it be coming from?
The far out explanations included lifts always being open somewhere... this was a little too improbable but sufficient reasoning till something better came along. The brain is tuned in to hearing the background radiation of creation. That is was just plain unscientific... we would have heard the big bang long ago then. Was it the hiss of electricity passing through the wiring around the house? Probably, but still, one should then hear all sorts of buzzing noises in the head...
Understandably then, a closer and more careful analysis of the "krrrrrrrr" was carried out, and the sound was concluded to be real. This must probably be the general ambient sound of the night. Maybe all the sounds that sounded in the night accumulated into a general planet-wide "krirrrrring" and it was just buried in the subconscious, just like many other sounds. The quest for the source of the "kirrrrrring" was prematurely abandoned.
So, one night, I am walking home, and am thinking of nothing in particular, when something beneath my shoes goes "crunch". I took a step back, look down and realise that I have stepped on a cricket.