Air & Noise Compliance

The Commonwealth of Massachusetts

Department of Environmental Protection (DEP)

Noise Control Regulation 310 CMR 7.10

 

The Commonwealth of Massachusetts has promulgated a noise policy in May of 1990.  This policy was never vetted through science or public opinion and is loosely based on two noise annoyance principles: Both substantial increases in sound level and discrete sound tones are very noticeable and generally considered annoying.

The DEP requires local communities to enforce the policy at the communities discretion. The policy is very poorly written from an acoustical perspective and is typically implemented with little understanding of the science behind sound control and measurement, including the acoustical, psychological and sociological factors. The policy is typically used to exempt noise sources from noise mitigation even though community members feel impacted. The DEP only enforces this policy on projects that trigger air quality permits and it has also exempted projects after they were challenged. All signs of poor regulation.

 

310 CMR 7.10  Noise

(1) No person owning, leasing, or controlling a source of sound shall willfully, negligently, or through failure to provide necessary equipment, service, or maintenance or to take necessary precautions cause, suffer, allow, or permit unnecessary emissions from said source of sound that may cause noise.

(2) 310 CMR 7.10(1) shall pertain to, but shall not be limited to, prolonged unattended sounding of burglar alarms, construction and demolition equipment which characteristically emit sound but which may be fitted and accommodated with equipment such as enclosures to suppress sound or may be operated in a manner so as to suppress sound, suppressible and preventable industrial and commercial sources of sound, and other man-made sounds that cause noise.

(3) 310 CMR 7.10(1) shall not apply to sounds emitted during and associated with:

  • parades, public gatherings, or sporting events, for which permits have been issued provided that said parades, public gatherings, or sporting events in one city or town do not cause noise in another city or town;
  • emergency police, fire, and ambulance vehicles;
  • police, fire, and civil and national defense activities;
  • domestic equipment such as lawn mowers and power saws between the hours of 7:00 A.M. and 9:00 P.M.

(4) 310 CMR 7.10(1) is subject to the enforcement provisions specified in 310 CMR 7.52.

The DEP has established a Noise Level Policy for implementing this regulation. The policy specifies that the ambient sound level, measured at the property line of the facility or at the nearest inhabited buildings, shall not be increased by more than 10 decibels weighted for the "A" scale [dB(A)] due to the sound from the facility during its operating hours.

The ambient sound level is the sound from all sources other than the particular sound of interest; also known as the background sound level. The ambient sound measurement (A-weighted sound level) is taken where the offending sound cannot be heard, or with the sound source shut-off. The ambient sound level is rarely found to be constant over time, and is usually quite variable. The ambient sound level is considered to be the level that is exceeded 90% of the time that the noise measurements are taken. The ambient sound level may also be established by other means with the consent of the DEP.

The dB(A) unit of sound measurement is altered (or weighted) to reflect human sound sensitivity. For instance, for those frequencies of sound which humans hear very well, the actual reading is enhanced, or increased, in the weighting process. The "weighted" reading therefore emphasizes the frequencies best heard by humans, and likewise de-emphasizes those sound frequencies which are less well heard.

The guideline further states that the facility shall not produce a pure-tone condition at the property line (or at the nearest inhabited buildings). A pure-tone exists if the sound pressure level, at any given octave band center frequency, exceeds the levels of the two adjacent octave bands by three (3) or more decibels.

The Massachusetts Department of Environmental Protection (DEP) adopted this Noise Control Regulation, 310 CMR 7.10, under the authority of M.G.L. Chapter 111, Section 142B and 142D. The Noise Control Regulation is used to limit the sound impact of new stationary sources and to respond to complaints of certain excessive sound. The DEP Noise Control Regulation can be enforced by local officials under the authority of 310 CMR7.52

310 CMR 7.52  Enforcement Provisions

"Any police department, fire department, board of health officials, or building inspector or his designee acting within his jurisdictional area is hereby authorized by the DEP to enforce, as provided in M.G.L. c. 111, S 142B, any regulation in which specific reference to 310 CMR 7.52 is cited."

Noise is defined in the Regulations as "...sound of sufficient intensity and/or duration as to cause or contribute to a condition of air pollution."

Community Sound Level Criteria

A source of sound will be considered to be in compliance with the DEP noise regulation 310 CMR 7.10(1) if the source does not:

  • Increase the broadband sound level by more than 10 dB(A) above ambient, or
  • Produce a pure tone condition.

 

************

Some comments on the DEP Noise Policy to consider

We have been using this policy for noise impact determinations since 1990 and it is been a very haphazard method for addressing community noise issues.  It is more commonly interpreted incorrectly from an acoustical (noise metric and methodology) perspective than done correctly. We see it being used as a shield and a weapon; but typically being inadequate in addressing the noise annoyance issue. The DEP noise policy works best at addressing steady noise sources such as mechanical systems that run continuously, although it may exempt audible tones which people find annoying.

What are some of the problems with the DEP noise policy:

  • Reasonableness cannot be defined by decibel criteria because reasonableness is subjective and decibel criteria are not.
  • No one decibel criterion or even multiple decibel criteria can properly regulate noise emissions from a subjective perception of any diverse community. The need for exceptions as an indicative response to this. The fact that regulation has been moved down to the lowest denominator (townships) is indicative of this. The difference in types of noise emissions is indicative of this. The fewer people involved in the perception is the greater the likelihood of agreement; particularly considering that a noise impact is an individual experience.
  • Community noise measurements and perception studies are all done using A-weighted sound levels. A-weighted sound levels represent the sound frequency distribution similar to the average human hearing; that’s how we hear sound. All sound level measurements, including frequency spectra for tone recognition, should be made using A‑weighted (dBA) sound levels.
  • The L90 is the sound level exceed 90 percent of the time; it is the quiet moment during the measurement period. The time period that should be used in a measurement is not defined. Short bursts of sound will not be apparent in the L90 at all. The Leq is typically used in community noise since it has some account for all sounds made during the measurement.
  • Sound levels 10 dBA greater than the L90 are commonly recorded during the same interval that the L90 is recorded. If the time period (interval) is 60 minutes, the L90 represents the sounds that were less for a 6 minute portion of that period. For the other 54 minutes, the sound will be greater and often greater than 10 dBA from the L90. The DEP Policy does not specifically state the 10 dB increase in future sound levels is an increase in the L90 and not a sound 10 dBA greater that occurs during the interval. It is the only reasonable assumption; which is not always being used even by acousticians. It makes modeling of the future sound levels much more complex since usage factors for time intermediacy are not necessarily valid. We have seen many poor modeling attempts which amount to a waste of money rather than proper disclosure.

  • Using whole-octaves to determine tonal noise issues and a minimum of 3 dB increase is inadequate. Tones are typically more frequency specific and 3 dB is often more than what causes general annoyance.  In general, any audible tone is typically potentially annoying.

  • One of the most important factors in measuring sound is the length of the analysis time-period. The DEP Policy offers no guidance so is anything plausible? The most commonly used community sound criteria use the one-hour Leq which by definition, as an energy-averaged level, is based on a time-period. Using an instantaneous sound level in general criteria is inappropriate since they are ever present and don’t consider quantity and duration.
  • A 10 dBA increase in sound level is perceived as a doubling in loudness by an average person and a substantial increase/decrease by acousticians. However, it does not consider the existing sound scape and whether more or less sound could be considered acceptable or not. It’s a concept that may not be appropriate for existing low-noise or high-noise environments.
  • The biggest problem we’ve encountered with the DEP Policy is it’s commonly used to fend-off noise complaints. If a project has a sound study saying it meets the DEP Policy, that statement is used against people who are claiming being disturbed by its sound emissions. No sound study can preclude noise impacts from occurring since noise impacts result from real-time operations/activities which were not necessarily or likely included in the studies. A study saying it is possible to be quiet is in no way a guarantee that noise impacts will not occur. Common differences from study to real life are as-built considerations which may include faulty designs and construction and operational characteristics which include systems not working properly or as modeled.