Bass Tire Facility, Tennessee

Location: Murfreesboro, Tennessee
Owner/Operator: Bass Tire Company Inc.

Bass Tire is a locally owned independent tire and automotive service company based in Nashville, Tennesse.

HGC Noise Vibration Acoustics was retained by Bass Tire to conduct a noise study for a proposed new automotive repair facility in Murfreesboro, Tennessee. A roughly 150’ by 60’ automotive repair facility was proposed for the site. The facility will include retail and office space on the north side of the building, and a repair facility with eight bays and various equipment at the south end.

HGC personnel investigated the acoustic environment surrounding the proposed facility to establish baseline sound levels for the purposes of determining compliance with the City’s sound level limits. Sound levels were measured and monitored over a six-day period.

The acoustic environment around the site is suburban in nature and the land is generally flat. There are existing residences to the south and east of the site. The land to the northeast of the site is vacant and to the west is a commercial property along with another vacant lot that was being developed for commercial use at time of the study. North of the site are several commercial properties, including an employment agency, a veterinary clinic, several restaurants, a nail salon, and an automotive repair facility.

A 4-lane roadway is the dominant source of traffic noise at the site with a 2-lane roadway representing a secondary source of noise.

The City of Murfreesboro Code of Ordinances, Chapter 21, Article V – Noise Control  (Murfreesboro Noise Ordinance) provides noise criteria for “Residential or noise-sensitive zones”, for “commercial zones” and for “industrial zones”.

Sound Level Limits

Neither the State of Tennessee, nor Rutherford County provide specific sound level limits applicable to the type of sound produced by the proposed facility. However, the Murfreesboro Noise Ordinance establishes sound level limits to: “…minimize the exposure of citizens to the potential negative physiological and psychological effects of excessive noise, to protect, promote and preserve the public health, safety and welfare, and to achieve these goals in a manner that promotes the use, value, and enjoyment of property, conduct of business, sleep and repose, and reduces unnecessary and excessive sound in the environment.”

Sound level limits have been developed by the City for residential and noise-sensitive areas, commercial areas, and industrial areas. These limits may apply anywhere on the property.

Separate limits are provided for steady sound and for sounds with special characteristics (Pure Tones, Cyclically Varying Sounds, and Quasi-Steady Sounds). The sound of an automotive impact driver is a quasi-steady sound, and thus the somewhat more restrictive sound level limits pertaining to these types of sounds were used in the assessment.

In addition to the general sound level limits, the City prohibits any sound whose equivalent A-weighted level exceeds the ambient level by at least 10 dBA during the daytime hours or by at least 5 dBA during the nighttime hours.

Noise Sources Description

It was anticipated that the new facility in Murfreesboro would provide the same services, have the same hours of operations, and contain similar sound sources as the existing Bass Tire facility located at in Nashville, Tennessee. Thus, the existing Nashville facility was visited by HGC staff to gain a better understand of the operations likely to occur at the proposed facility, and to conduct sound level measurements of those activities for use in the acoustic model.

During the site visit, observations were made to establish the dominant noise sources, the typical duty cycle of noisy activities, the typically bay usage, and the locations where equipment was used. This information, together with drawings, specifications, and other information about the new facility, was then used to build an acoustical model of the new facility.

Stationary Source Assessment

Predictive noise modelling was undertaken to predict and assess the sound levels from the proposed facility at the closest receivers. The noise prediction model was based on sound emission levels of the assumed operational profiles (during the day and night), and established engineering methods for the prediction of outdoor sound propagation. These methods include the effects of distance, air absorption, and acoustical screening by barrier obstacles.

A combination of sound power levels measured from the Bass Tire facility in Nashville and other data collected during the visit data obtained from similar projects undertaken in the past by HGC were used in the analysis

Acoustical Barriers

To mitigate the impact of the sound from the proposed facility on the nearest noise receivers, the construction of two acoustical barriers was recommended. With the implementation of these recommended acoustical barriers, sound levels from the modeled operational scenario were predicted to meet the applicable sound level limits specified in the City of Murfreesboro Code of Ordinances, Section 21, Article V – Noise Control at the nearest receivers.

Acoustical consulting services delivered:

• Acoustic Assessment Report in accordance with City of Murfreesboro Noise Ordinance
• Comprehensive onsite and offsite acoustical measurements
• Predictive acoustical modeling
• Developed noise barrier specifications for inclusion in the site development plans