I connected my phone line to an audio mixer. When connected to the mixer,
I can hear any signals that get sent over the line, including conversations.
Mysteriously I'm noticing noises that happen when no phones are in use:

1) Every time I hang up a phone, I, almost immediately, will hear a series
of two chirps on the phone line. The tones are approximately 250ms apart
and approximately 250ms in duration. Each chirp sounds like a "dual" tone,
like maybe a type of sound a modem sometimes makes, but the prominent
frequency of the 1st chirp is roughly a C# above A=440 and the second is a
above A 440 (approximately two semitones apart, with the first being around
554hz and second being around 587.83 assuming I don't have the octave
wrong). The chirps happen every once in a while no phones are in use in
addition to happening every time the phone is hung up.

2) There are humming noises that happen virtually all the time, mainly
resembling a 60hz hum but can jump up to the next octave and vary in pitch.
The humming noises are generally lower in volume than a quiet phone
conversation.

3) Every once and a while there is a buzzing that resembles a ringer signal
albeit weaker and which doesn't always repeat at regular intervals like a
ringer signal.

4) There are buzzes that resemble a cat purring every once and a while.

5) When connected to the mixer, my phone line will often disconnect or stop
ringing after the first ring when somebody calls me...why does this happen?
(otherwise there is no interference with the phone line or DSL)

NOTE: I have DSL, but the noises happen whether or not my DSL modem is
turned on. I am monitoring from a jack that has a DSL filter connected to
it, so the DSL should be filtered out in any case.

NOTE2: The noises happen whether or not any particular phone is connected to
the phone line.

Are these normal noises, or is it likely that my phone is tapped?

Granted, I have no reason to believe anyone would want to tap my phone line
since I lead a very boring life, however since I'm not the original owner of
my house, I decided to check for "bugs" on my gray phone interface box on
the owner side of the box. None were present. I did not open the phone
company's side of the box, however.

Wondering what these noises are? Clearly the two chirps when the phone is
hung up is not just "line noise".

Thanks,

J.