How Sontech helped a European municipality reduce operator cab noise in a municipal tractor below the 85 dB(A) threshold.
A European municipality operated a small tractor and implement carrier for municipal maintenance work. During loaded driving, the noise level in the operator cab was measured at 86 dB(A) – exceeding the recommended limit of 85 dB(A).
Prolonged exposure to noise above 85 dB(A) increases the risk of hearing damage, tinnitus and fatigue. For the operator, this represented a daily health hazard, and for the municipality, an occupational health issue that needed to be resolved.
The cab had already been partially treated with Acusticab 19 SA in the ceiling, rear pillars and sides, along with a heavy floor mat (13 kg/m²). Despite this, the noise limit was exceeded. The source of the remaining noise needed to be identified and addressed.
Sontech performed an acoustic analysis of the cab and identified two primary noise transmission paths: the hydrostat and the instrument panel. Targeted measures were implemented to treat these areas.
The hydrostat was treated with a rubber mat and AC 30 S (30 mm self-adhesive sound absorbent). The sealing over the lever to the hydrostat was improved to eliminate airborne noise leakage.
The instrument cover was treated with AC 30 S combined with ISO 7 (bitumen-based insulation, 7.5 kg/m²) on the back of the instrument panel. This reduced both airborne and structure-borne noise.
30 mm self-adhesive air sound absorbent. Effective damping of mid- and high-frequency airborne noise in confined spaces.
Bitumen-based insulation with a surface weight of 7.5 kg/m². Provides mass-based sound damping and vibration reduction on thin sheet metal and panel structures.
19 mm self-adhesive air sound absorbent. Already installed in the ceiling, rear pillars and sides as the cab baseline treatment.
After treatment, the noise level was re-measured during loaded driving with the microphone positioned at the operator’s right ear (Brüel&Kjær type 2230 with octave and third-octave filters type 1625).
Professional noise measurement in the cab using calibrated equipment according to standard.
Identification of noise sources and transmission paths, and design of the right treatment package.
AC 30 S, ISO 7 and Acusticab 19 SA – the right material for the right application.
Post-treatment measurement confirming the noise level dropped below the 85 dB(A) limit.
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