I live in a populated forest in the Sierra Nevada mountains. There is
a house somewhere in my forest that plays music all night long,
virtually every night.  The low frequency bass vibrations from this
music come right through the walls of my house.  It is profoundly
annoying, stressful and interferes with my ability to sleep.  I have
tried to find the source of this noise by going down many of the
nearby streets and listening.  Even though I am still able to hear the
low frequency sound vibrations, I have been unable to locate the
source of the sound.  It seems to be coming from everywhere and
nowhere at the same time.  My neighbor has heard these sounds and has
occasionally gone out to try to locate the source as well.  But he has
not been able to find it, either.  I have called the police, but they
were unable to hear the noise, which seems typical if one is not
accustomed to hearing it.  How far away could the source of these
sounds be?  Are there any devices or instruments that are effective in
identifying the source of  long-frequency sound waves such as those
produced by a music stereo system?

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Clarification of Question by laketahoeblue-ga on 20 Oct 2004 01:17 PDT

Responses to issues raised in other replies:  I belive the low
frequency noise is definitely from amplified music. It thumps to a
bass-like beat.  However, the "beat" varies somewhat in it's pattern
every few minutes.  There are often slight gaps in the noise every
three to four minutes....

Basement suggestion is an intersting thought.  Basements are not
normal features in rural California homes built in the last 20 years,
but some homes are built with them.....

I appreciate all the ideas people have shared. Thanks.

Yes! There are such things.

Here in the UK, they used to be called RDF - Radio Detection or
Direction (?) Finders. Maybe they still are.

Typically you can set up two receivers some way apart; find the
strongest signals and triangulate the results.

Good Luck: It must be VERY annoying!

Here you go:

http://encyclopedia.thefreedictionary.com/Radio%20direction%20finder

It appears you only need one RDF unit but you will need a special aerial.

An RDF isn't going to help poor "Sleepless in the Sierra";  the
offending signal is an acoustic wave, not an electromagnetic wave.  A
*Radio* Direction Finder is only going to work for electromagnetic
signals!

Locating the source of Low Frequency Noise (LFN) is not easy, as you
have found.  Some of the reasons for this are given at
http://www.epa.ie/FAQs/Noise/LowFrequency/.

Presumably, the signal is being transmitted primarily through the air
(rather than coupling to the ground).  Have you tried to look for a
correlation between the wind direction and the times you hear the
noise?  That might give you a clue as to the general direction to look
for the source (i.e., the source is likely to be upwind).

If you could find a sound pressure meter that incorporated a low-pass
filter, you might be able to go out on a very still (windless) night
and try to survey the intensity of the sound as a function of position
by driving around.  The sound levels should obviously be higher as one
gets nearer the source.

Interesting.  I read the article at
http://www.epa.ie/FAQs/Noise/LowFrequency/Answer,2093,en.html, and it
occurred to me that perhaps the article assumes that one is using an
omni-directional microphone.  What if you used a very sensitive
uni-directional microphone, e.g., a parabolic mic or a "shotgun" mic,
and stood in your yard at night moving in a very slow circle listening
for the noise.  You could even mount the mic on a tripod to lessen the
effect of vibrations or other noise introduced by your body. 
Presumably the reflections and diffractions would be ignored by the
directional mic, since they are likely not coming directly from the
sound source.  (In other words, if the shotgun mic is not pointed at
the source, it would not hear the noise since the reflections and
diffractions are likely not "coherent," as they must be for the
shotgun mic to hear them clearly).  Once you have pinpointed the
direction, walk in a straight line toward the sound (perhaps using a
GPS to record exact coordinates and waypoints) until you find the
source.

My commiseration. The Sierra Nevada -- that?ll be Spain then.

Unfortunately, unidirectional microphones (such as shotgun) are poorly
directional at low frequency unless exceptionally long. Same applies
to parabolic unless *huge*. For similar reasons, ears are poor at low
frequency too. Britain detected sub-sonic shell reports across the
English Channel in WW1 (or was it WW2?) with building sized
microphones, the sensing element being a hot wire. Your problem is
similar.

Notes on dish size :-
http://www.unipv.it/webcib/instru.html

The problem may of course be exacerbated by your room dimensions
causing resonance. Very difficult to absorb low frequencies. Since it
would appear that the effect is almost subliminal, one could in theory
monitor with an extended response microphone, narrow band processed
(ideally) by DSP. You could then detect if you were getting closer.
But that is a truly horrid prospect unless you know a very good
engineer who owes you a big favour.

One suggestion though. On the basis of how the sound seems to arrive,
I would suspect that it is emanating from a basement -- a much loved
hangout for the socially naive ;-)

Best

As noted above, trying to find the source of a low-frequency sound
with a single measurement position is extremely difficult due to the
long wavelengths involved. At a minimum, you'll need some kind of
triangulation, and even that is not easy. As an example, consultants
have been trying to find the source of the Kokomo Hum for years not
(http://tinyurl.com/3qtg8), and have only recently made headway.

What you could try doing is renting a real-time analyzer (or hiring a
consultant) to identify the frequency of the tone. Once you know the
frequency involved, you may be able to correlate it with machinery or
activities at nearby facilities.

Occurred to me last night, are you absolutely sure it is music?
But'anechoic-ga' beat me to it :-)

Might it be machinery which gives out low frequency noise such as a
generator, especially if ?hunting? rhythmically?

Best

That does indeed have the signature of music. Tiny chance it could be
emanating from underground pipes with a duff pumping system.

However, have you tried the ?ear to the ground?? Best on a hard flat
surface, preferably not in the middle of the highway. If you can hear
the noise through the ground you might be able to contact mike it.
Cheap piezo disks do quite a good job in this sort of application if
suitably amplified. Need a low pass or preferably band pass filter
too. Then you might be able to display on a battery powered
oscilloscope (readily hired). That being so, use two mikes separated
by a good few meters, display on two traces and look for phase
difference. Swing one of the mikes in an arc to point of max phase
difference and follow up in that direction -- not 180 degrees in the
wrong direction of course.

Police won?t be inclined to hear it ;-) Dunno what the situation is in
the States, but local authorities may have usable legislation on
?public nuisance?.

Best

this is possibly a beat phenomenon between two different higher
frequencies that are close to eachother see for example

I. Rushforth, A. Moorhouse, P. Styles, ?A Case Study of Low Frequency
Noise Assessed Using DIN 45680 Criteria?, Journal of Low Frequency
Noise, Vibration and Active Control 21, 4 (2002) pp. 181-198.

if you want to try to duplicate these effects from your computer use a tone
generator, e.g., http://www.esser.u-net.com/ttg.htm 

a simpler tone generator for you to use is 
http://www.mindspring.com/~scottr/zmusic/ Try 200-Hz and 230-Hz
looping at the same time

notice that both high frequencies combine to give you a beat

if this is a beat problem, most likely something in your house is
providing one of the frequencies ... if you can do so safely, turn off
all rotary devices in your home, the next time you hear this effect
(including: fridge, furnace, AC, washing machine, dryer, anything that
generates noise via rotation)

Hi
I am suffering from a similar problem. It is for sure rap music, 
coming from a basement.  I live in a rowhouse directly next door. Ear
plugs do not stop the noise, It feels like I am "hearing it" through
my skin. Is there a way to insulate myself from this annoyance?