Pssst! my car has a secret and i'm dying to know

there’s something wrong w/ my 99 Nissan Altima. it keeps whispering to me, “pssst, there’s something wrong w/ me,” but it doesn’t want to give me any details. my trusty reliable mechanic has given it a complete once over, drove it, put it on the electronic diagnostic system, NOTHING. the frequency and length of the psssssst is increasing week by week. it’s been going on for months. it makes the sound once , w/i 2 min of driving, often on or immediately after an acceleration. it can whisper to me 3 times in 5 minutes, or not whisper for hours (then again, that might be when my music is too loud) i’m worried about my car, please tell me it’s secret!

“please tell me it’s secret”

Okay, here goes! It’s secret.

Seriously, however, you have provided very little information for us to use in attempting to diagnose this problem. Please post back with information such as:

Odometer mileage?
Has the car been maintained in strict accordance with the manufacturer’s maintenance schedule?
Automatic transmission or manual transmission?
Is the noise dependent upon ambient temperature?
Is the noise dependent upon the engine temperature?
Is the noise dependent upon vehicle speed?
Is the noise dependent upon use of the brake pedal?
Is the noise dependent upon turning the steering wheel?
Is the noise dependent upon use of the air conditioner?

Take a rider along for the test drive to listen and pinpoint. Does the car have automatic temp control a/c ? I wonder if it’s related to the actions of the a/c system.

completely car and a/c system ignorant, but the problem does occur in the winter as well. it’s been going on since January

120,000 miles, automatic. oil change and all other maintenance pretty much on scdl. struts and all brakes less than a year old. an 02 sensor changed in 2003. the noise doesn’t seem dependant on temp - ambient or engine, nor speed, definitely not brake pedal or steering wheel, don’t know for sure if i’ve tried experimenting w/ no a/c or heat on… i’ll do that when i head out later today.
it DOES seem to occur more during acceleration, or immediately thereafter… (thank you for asking the right questions. i’ve never posted a car question)

i’ve been in the car w/ my mechanic during the test drive. he hears it, but can’t pinpoint it!

so when i don’t use the a/c, my car doesn’t whisper “pssst” which definitely narrows things down a bit. any specific ideas - is it the actual a/c system that has a problem, or is the a/c placing a demand on something which is having the problem? think i’ll head back to my mechanic w/ this new clue to see if he can find it now.

Since the a/c compressor runs when the hvac system in in the Defrost mode–even in the winter–this could still be related to the a/c system.