 |
Wheel Howl (not squeal)
Author: Edward
Date: 12-31-2013 - 17:58
While BART certainly has wheel squeal on sharp curves, as any solid axle wheel set can produce, the main and characteristic noise is wheel howl.
Wheel Noise Report
From page 54 (61 in the pdf):
4.3 CURVING NOISE
Curving noise includes both normal rolling noise, which
also occurs at tangent track, and noise unique to curving,
resulting form (sic) lateral slip of the wheel tread across the rail
head. Noise due to lateral slip is often manifested as an intense,
sustained squeal, caused by the negative damping associated
with the friction versus creep characteristic. Normal rolling
noise will not be significant at short radius curves, especially
in the presence of wheel squeal, due to low train speed, and at
high-speed curves, rolling noise may be treated in much the
same manner as for tangent track. This section is directed
entirely to curving noise due to lateral slip generated noise.
There appear to be two types of curving noise. The first
and most prevalent is wheel squeal cause by sustained nonlinear
lateral oscillation of the wheel. The second, less obvious,
and less common, is wheel howl, which may be due to the resonant
but unsaturated response of the wheel to dynamic lateral
creep forces. There are reasons to believe that these types of
curving noise are separate phenomena: (1) they do not sound
the same; (2) wheel howl at curves increases with train speed,
while conventional wheel squeal may disappear with sufficiently
high train speed; and (3) wheel/rail howl may be closely
associated with short pitch corrugation at curves. Of these two
types of curving noise, wheel squeal is the more prevalent,
while wheel howl may be limited to lightly damped aluminum
centered wheels such as used at BART. In fact, wheel howl
may be unique to BART, because BART is the only transit system
employing rigid aluminum centered wheels.
Elsewhere in this report wheel howl on tangent track is linked to rail corrugations. Any BART rider knows that one doesn't need a curve to get wheel howl, unlike wheel squeal.
Wheel Noise Report
From page 54 (61 in the pdf):
4.3 CURVING NOISE
Curving noise includes both normal rolling noise, which
also occurs at tangent track, and noise unique to curving,
resulting form (sic) lateral slip of the wheel tread across the rail
head. Noise due to lateral slip is often manifested as an intense,
sustained squeal, caused by the negative damping associated
with the friction versus creep characteristic. Normal rolling
noise will not be significant at short radius curves, especially
in the presence of wheel squeal, due to low train speed, and at
high-speed curves, rolling noise may be treated in much the
same manner as for tangent track. This section is directed
entirely to curving noise due to lateral slip generated noise.
There appear to be two types of curving noise. The first
and most prevalent is wheel squeal cause by sustained nonlinear
lateral oscillation of the wheel. The second, less obvious,
and less common, is wheel howl, which may be due to the resonant
but unsaturated response of the wheel to dynamic lateral
creep forces. There are reasons to believe that these types of
curving noise are separate phenomena: (1) they do not sound
the same; (2) wheel howl at curves increases with train speed,
while conventional wheel squeal may disappear with sufficiently
high train speed; and (3) wheel/rail howl may be closely
associated with short pitch corrugation at curves. Of these two
types of curving noise, wheel squeal is the more prevalent,
while wheel howl may be limited to lightly damped aluminum
centered wheels such as used at BART. In fact, wheel howl
may be unique to BART, because BART is the only transit system
employing rigid aluminum centered wheels.
Elsewhere in this report wheel howl on tangent track is linked to rail corrugations. Any BART rider knows that one doesn't need a curve to get wheel howl, unlike wheel squeal.
