[Ed Anson]

wrote:
Problem:
Our house in the city shares a common wall with our neighbor. At the
back of the house, our dryer vent is positioned about 8 feet from
this
common wall. Nothing is wrong with the dryer according to a repair-
person and anyone's casual observation. The vent pipe is not
obstructed at any point. The exhaust vent fan (or dryer blower?)
does
make a typical "whirring" noise which escapes from the vent and
resonates in a way which disturbs the neighbor. As crazy as it
seems,
I now believe it's a legitimate problem for them due to the
configuration of the buildings and back yard.

There are two other possibilities you ought to check:

1. The noise might be propagating through the wall. Depending on
construction, some walls are quite capable of transmitting sound. If
that turns out to be the case, just a bit of foam or something where the
vent passes through the wall might fix the problem.

2. If something is indeed resonating, changing its size (and thus its
resonant frequency) might help.