Usually, the sound presents for many reasons. High pressure, low pressure, and auto shut failer after 5 years.
Reason 1:
Incoming High pressure water is more than 75 psi, add pressure reducer. Part #105229
Reason 2:
Low incoming water pressure less than 50 PSI check city water incoming pressure to the system membrane housing inlet. if it's less than 50 PSI check the pre-filters as they might be clogged with dirt. The pressure is well and more than 50 PSI check the membrane if it's more than 2 years replace it. if all above is good and city water is less than 50 PSI then you have to add a booster pump to increase the pressure by more than 60 PSI
Reason 3:
Check the flow restrictor if partially blocked with the dirt during the use by Appling water pressure from the opposite side.
Reason 5:
If the auto shut-off valve is older than 7 years its better to change it by searching item #105111
