Gas Turbine Handbook : Principles and Practices

Gas Turbine Acoustics and Noise Control 145
Chapter 10
Combustion Turbine
Acoustics and Noise Control
COMBUSTION TURBINES—
LOTS OF POWER IN A LITTLE SPACE
Avery attractive attribute about combustion turbines is the
modular packaging of these units for fairly rapid delivery
and installation. Some OEMs or other packagers package the
units to produce no more than a certain sound level at 400 feet (or at
some standard distance) from the site, but multiple units co-located
and combined with other sources of noise can cause some difficulty
in determining the total sound level at a location. The complexity of
combustion turbine systems and their ancillary equipment generally
requires an acoustical engineer well experienced with such systems
to fully analyze the acoustical emissions and make a determination
whether the expected sound levels meet regulatory requirements, are
in balance with the environment or community, or need some level of
noise mitigation. Industrial combustion turbines are built as compact
high power delivery systems and the only place available to reduce
the noise is by adding on duct-silencing equipment to the front and
rear of the turbine system, which requires real estate and hardware
that increase cost. Technological advances over the last two decades
have given designers more tools and materials to develop some significant
noise control breakthroughs but these engines still produce
significant noise levels that must be mitigated or reduced to make
these engines compatible with either environmental or occupational
regulatory noise requirements. Combustion turbines typically have
inlet (compressor end) and exhaust (turbine end) total sound power
levels ranging from 120 decibels (dB) to over 155 dB. A reduction of
20-30 dB is fairly easy, 30-50 is typical of most silencer installations,
145