Inspect the mounting arrangement without adding unapproved material to the heater.
If a LAVA panel develops a persistent buzz, switch it off and let it cool before inspecting the mounting arrangement. Do not handle or adjust it while powered or hot.
The LAVA manual requires the supplied mounting components, a flat supporting wall and correctly secured mounting brackets. Have a qualified installer check that the panel is properly seated, its brackets and fasteners are secure, and it is not being strained by an uneven surface or interference with another object.
Do not insert felt, foam or another improvised spacer behind the panel as a general repair. Use only a model-specific remedy confirmed by the manufacturer. The existing brackets, ventilation and clearances must be preserved.
If the mounting is correct and the noise persists, or if there is flickering, a burning smell, damage or repeated circuit tripping, leave the panel off and contact WarmlyYours technical support at (800) 875-5285 with the model and serial number.
Source: LAVA installation manual (Safety, Scope of Delivery and Wall Mounting).