This provision is an "objective emission" control. Unlike the Tampering provision, this is specific to motor vehicles. It requires that a vehicle muffler not create more sound than the original equipment which has been measured. It prohibits any modification or replacement that increases the sound emission beyond that of the original equipment. It prohibits the sale of mufflers that do not meet original equipment standards. Many states have requirements that a muffler "shall be in good working order" which is not specific enough. California (Section 27150.1)) requires that a retail seller that sells a product in violation of the muffler regulation must install a replacement muffler that meets the regulation and must reimburse the purchaser for the expense of replacement.