RV Generator Noise
RV Generator noise plagues RV parks and even some residential neighborhoods. To stop RV generator noise, one must first understand what it is, where it is coming from and only THEN can a solution be implemented. See SOUNDPROOFING AN RV GENERATOR.
Generators produce noise across the audible spectrum from numerous airborne and structureborne sources. A review of some of these noise sources is provided below:
- Fan Noise – Water-cooled generators will have a cooling fan and radiator. The fan will emit pure tones at the fan blade pass frequency and its harmonics. Typical blade pass frequencies will be in the 120 – 160 Hz range. Fan noise can propagate through openings or gaps in the generator compartment or directly through the generator enclosure if there is not adequate sound proofing installed in the panels.
- Exhaust & Inlet Noise – Generators that do not have adequate exhaust mufflers or intake plenums will emit low frequency noise at the engine firing frequency. Exhaust pipes will typically pass through the generator compartment and will be connected to a muffler that is located underneath the RV. If the end of the exhaust pipe does not extend beyond the passenger compartment, pressure pulsations from the exhaust may be heard inside the RV. The inlet air plenum may or may not include a muffler and is typically located within the generator enclosure.
- Engine Noise – The combustion impulses during operation of the engine excites resonances of the engine block pistons and valve train that are heard as a high frequency “ringing” or “pinging” noise at the engine firing frequency. This noise radiates in all directions, however, it is more prevalent on the bottom of the engine when it passes through the relatively thin sheet metal of the oil pan. If there is a resilient structure underneath the generator, noise from the oil pan will reflect off of this structure and reverberate within the generator compartment.
- Mount Noise – The generator will have periodic vibrations at the rotational speed of the motor and at the engine firing frequency. These vibrations should be damped by the generator vibration isolation mounts, however, it is not always possible to tune the mounts for vibration control at the motor operational speed. This is due to the fact that the mounts must also isolate the generator for road vibrations, requiring stiffer mounts. Vibrations from the generator can therefore be passed into the structure of the generator compartment, causing panels to vibrate at their natural frequencies and radiate noise like loudspeakers.
- Exhaust and Cable Grounding Noise – The exhaust system and electrical cables are typically held in place using elastomeric mounts or grommets that are supposed to isolate vibrations from the engine from the generator compartment. During transportation, it is possible for these vibration mounts to become misaligned, resulting in the exhaust system or cables contacting the structure of the generator compartment or RV. RV generator noise due to grounded exhaust pipes or cables can pass directly through the body of the RV and into the passenger compartment. This noise typically sounds like a low freqency “moaning”.
A typical RV generator compartment will consist of sheet metal walls on all sides, with an outside cover with a screen to allow for the flow of cooling and induction air.
The generator is then installed within the compartment and bolted into place. The compartment will typically have minimal or basic soundproofing materials installed from the factory. The hard walls within the compartment can act like a sound box, where noise from the generator is reflected and amplified. This sound and vibration can pass through the walls of the generator compartment directly into the RV and disturb its occupants or it can escape through numerous open airflow paths into the environment and disturb neighbors.
Sonic-Shield can assist RV owners throughout the soundproofing process by identifying the source(s) of the noise problem(s) and the noise transmission path(s).
Deadening RV generator noise used to be difficult. No longer! Sonic-Shield has an engineering staff with advanced technical capabilities who can assist RV owners in the selection and installation of soundproofing materials and products to reduce RV generator noise and vibration problems from their generators.