Mr. Skeeter. Unfortunately hydraulic and pneumatic applied physics does not directly translate to your field of endeavor consisting primarily of electronic binary transmission and metalanguage. You will be required to physically examine all plumbing terminations to determine the likely candidates for modification when required. In regard to the pressure modification, the services of an adequately prepared professional, such as a Licensed Master Plumber are required. I have observed that a Mr. Bungie uses pressure regulation as a standard practice in his locale. Also a Mr. Sylvan specifies and recommends certain means for air removal at the point of the domestic hot water appliance. Once these parameters have been changed, the sound should attenuate to the satisfaction of you and yours.