Noise and vibration problems

For the procedures and standards of noise and vibrations measurements we refer to the documents ISO/WD 8579-1 for sound and ISO/WD 8579-2 for vibration. The methodology for the determination of the sound level is determined in the ISO document ISO 3743-1-2/3744/9614-1-2. The ISO/WD 8579-2 takes the standard ANSI/AGMA 6000-B96 over. For the analysis of the vibration and noise problems all characteristics of gears and bearings must be known. As it usually concerns comparative measurements, it is necessary to know upfront the initial sound and vibration value in order to draw up a reliable analysis. The following are some practical tips to reduce sound and vibration level. However, these tips should be integrated from the beginning to avoid troubles afterwards.

Use high precision gears

Reduces the pitch errors, tooth profile errors and eccentricity errors. Grinded teeth increases the accuracy and the gear quality.

Use gears with a better gear quality

Grinding, lapping and honing of the tooth surfaces and initial wear of the gears increases the gear quality and reduces noise.

Ensure the correct tooth contact

Barreling can avoid edge contacts.
Specific tooth shape corrections can also be efficiently.

Typical backlash

A smaller backlash reduces the pulsating operation in a transmission.
A greater backlash usually gives less problems.

Increase the contact ratio

The larger the contact ratio the lower the noise level. By reducing the pressure angle or enlarging the tooth depth a greater contact ratio is obtained. Increasing the overlap quotiënt gives less sound. By this phenomenon gears with helical teeth produce less noise than gears with straight teeth; spiral bevel are also lower in noise than bevel gears with straight teeth.

Use smaller gears

Apply smaller moduli and smaller gear diameters.

Use sturdy gears

Strengthen the gear construction that gives more firmness and thus reduces the sound. Strengthen the housing and the shafts.

Use damping material

Synthetic gears give a lower sound with light loads and smaller rotation speeds.
Cast iron wheels produce slightly less noise than steel gears.

Use enough lubrication

Lubricate the gears sufficiently.
The use of high lubrication viscosity reduces noise.

Lower load and rotation speeds

Low rotational speeds and loads decrease the sound.

The following chart shows the acoustic power measured according to DIN45635, in function of the power transfer. The right-hand scale demonstrates the acoustic power measured at respectively 1 m and 3 m of the gearbox.

Vibrations are partially the result of imbalance in rotating parts. The following table shows you the quality level of imbalance again per type of machine according to ISO1940. The table below returns the permissible rest imbalance value for turning pieces according to the required quality level and in function of the rotational speed per minute.

Rate eω in
mm/sec
Rotor type – General examples
G4000 4000 Crankshaft combination of permanently installed marine diesel engines with low rotational speed and an odd number of cylinders.
G1600 1600 Crankshaft combinations of permanently installed two-stroke engines with large power.
G630 630 Crankshaft combination of permanently installed four-stroke engines. Crankshaft combination of elastic established marine diesel engines.
G250 250 Crankshaft combinations of permanently installed, fast-running 4 cylinder diesel engines
G100 100 Crankshaft combination of permanently installed, fast-running diesel engine with six cylinders and more; complete engines for passenger cars and trucks as well as for locomotives.
G40 40 Car wheels, rims, wheel sets, cardan shafts; crankshaft combinations of elastic drawn up fast-running four-stroke engines with six cylinders and more; crankshaft combination of the engines for passenger cars and trucks as well as for locomotives.
G16 16 Cardan shafts with special requirements; parts of crushers and agricultural equipment; parts of the crankshaft combinations of engines for passenger cars and trucks as well as for locomotives; crankshaft combinations of engines with six cylinders and more with special requirements.
G6,3 6,3 Process engineering equipment; drums for centrifuges; fans, flywheels, centrifugal pumps; parts for mechanical engineering and for tool machines; anchors of standard electric motors. Components of crankshaft combinations, with special requirements.
G2,5 2,5 Rotors of jet engines, gas turbines and steam turbines, turbo fans, turbo generators; drives for machine tools. Anchors of medium and large electric motors, with special requirements; anchors of small motors, pumps with turbine propulsion.
G1 1 Drives for image recorders and gramophones. Drives for grinding machines, anchors of small engines, with special requirements.
G0,4 0,4 Anchors, shafts and grinding wheels for precision grinding machines, gyroscopes.