Hello H20andSand, While we don't know the model of your vac, this muffler diffuser reduces air noise by about 10 percent. In addition, different RIDGID vacs have different decibel rating and these ratings were obtained with the hose attached to the vac during our tests. The sound pressure (dB level) of the machine likely doesn’t change much, but the tones (low verses high) can change from hose to hose. Most of the high dB noise is created by the machine but, again, each hose and the air rushing through it may create their own separate tones. Additionally, there have been some instances where a given hose may create a “harmonic whistle.” This noise is normally very high pitched and includes a higher dB reading than the vacuum. This isn’t normal for most hose/vacuum combinations, but there’s something in the way the hose was molded, the way the hose ends are attached, the length of the hose, the diameter of the hose, the way that hose is held or is laying, the way the air is moving through the hose and at what rate that air is moving that all combine to create this “whistle”. On a different note, the use of the adapter varies depending on the model of the vac. We have vac models with 2-1/2" hose and accessories that do not require the use of the adapter with the red clip. With that being said, specifically for your WD4070, the red clip adapter is not required to be used when attaching this muffer diffuser to the exhaust port. Lastly, we appreciate your feedback and all your comments regarding this vac. If you have questions or concerns, you may call our Customer Service at 1-800-474-3443 from Monday to Friday between 8:00 AM to 5:00 PM Central Time and we'll be glad to assist you. Thanks, RIDGID