A new concrete mould vibrator had been designed for the automated manufacture of a new building product and was due to be installed on the production lines of several sites. During prototype testing, the Buy Quiet process revealed that it produced 99dB(A), an unacceptable hearing damage risk.
Analysis of the machine noise and vibration showed the noise problem was caused by high frequency vibration radiated as noise by the machine frame with only a proportion of the vibration reaching the product.
Vibratory table modifications were designed to change the natural frequencies of the structure and to damp spurious high frequency vibration did not contribute to the compaction of the concrete in the moulds. This amplified the low frequency vibration fed into the product whilst reducing the high frequency vibration that was the source of the high noise levels.
The result was a noise reduction of 15dB(A) from 99dB(A)Leq down to 84dB(A) with the octave band levels shown here. Note the increase at 31.5Hz responsible for the increased productivity...
The cost of implementi ng the recommended modifications on the production machines negligible. In addition:
- productivity was increased by 25% (reduced cycle time)
- power consumption was reduced.
- reduced maintenance (less component stress, elimination of fatigue cracking)
This was an elegant engineering alternative to what would have been a costly and operationally disastrous acoustic enclosure.
A carbon negative noise control project.
