Noise testing is performed for the following reasons:
• To verify the ability of equipment to withstand its external
acoustic environment without unacceptable reduction in its
functionality and/or structural integrity.
• To measure the noise generated by the equipment.
External Noise Environment
Equipment may be subjected to an external generated noise environment
when the unit is located in areas such as adjacent to jet exhausts.
Measurement of Self-generated Noise
To determine the noise characteristics of equipment measurement of
the acoustic output is performed. The noise generated by equipment is
of two types:
• Airborne noise is that which is produced by a source that
radiates directly into the air. The airborne sound waves are
transmitted by pressure fluctuations in the air.
• Structureborne noise occurs when items are set into vibratory
motion by equipment noise sources. The vibrational energy is
consequently transmitted throughout the structure where it will
force various surfaces to vibrate. The vibrating surfaces in
turn transmit their motion to the air causing pressure
fluctuations that are then propagated as airborne noise.
However, during testing usually only the equipment vibration is