NORWEGIAN State Railway is planning to equip five of its locomotives with an innovative system to reduce noise in the driving cabs. The move follows a trial with a prototype developed by Silence International of Oslo, which was part-funded by NSB. This was tested for four months on a Di4 diesel loco between Trondheim and Bodø.
Silent Zone is primarily intended to deal with low-frequency long-wavelength noise, which is difficult to eliminate through mechanical methods and is known to have a particularly tiring effect at night or over longer distances.
Two loudspeakers are fitted to the headrest of the driver’s seat, around 100mm from each ear. Small microphones pick up incoming noise, which is processed by a patented microprocessor circuit. After about 50 ms, a similar sound is broadcast in anti-phase, which effectively cancels out the noise.
The equipment creates an oval ’silent zone’ around the driver’s head. Under normal driving conditions, the driver would remain within that zone for around 90% of the time.
Silence International, Norway
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