Touch upâs should be done minimum 4-6 weeks post the initial treatment. This allows time for eyebrows to heal fully before perfecting them for the second time. Free touch-ups are only valid up to 3 months from initial procedure date.
Re: The Tinny sound? Most folks that are concerned about a tinny noise with aluminum boats are referring to the noise generated by the hull moving through the water (which can be modulated/reduced through many different avenues). You mention vibration and rpms, so I'm guessing that you're not referring to that sound.
Damage to the inner ear from ageing or exposure to loud noise is the most common cause.This condition is often associated with tinnitus (buzzing, ringing or whistling noises in the ears) and distortion, so that a pure tone may be split or jangling.