CAJA offers expert assistance in transportation and community noise assessment and mitigation, including:

• On-Site Noise Measurement
• Residential Noise Studies and Sound Insulation Analysis
• Construction Noise Measurement, Analysis, and Mitigation
• Community Noise Surveys
• Traffic Noise Analysis Training
• Traffic, Rail, and Aviation Noise Measurement, Analysis, and Abatement Design

CAJA utilizes several of the latest noise modeling practices and techniques to accurately and precisely quantify ambient noise levels both prior to construction and after project completion.

Noise Monitoring
The first step in quantifying the impact a particular project may have on the existing noise environment is identifying the baseline noise conditions. CAJA's technical experts record existing ambient noise levels using the Larson-Davis 820 noise meter. The Model 820's measurement capabilities include instantaneous Sound Pressure Level; Lmin; Lmax; Lpeak and Unweighted Peak Levels; Ln (statistics); Leq; Sound Exposure Level (SEL); and Time Weighted Average (TWA). All of these parameters are measured simultaneously, making this tool very flexible in many different applications.

Construction Noise
To determine a project's potential construction-related noise impacts, CAJA uses a set of standards developed by the United States Environmental Protection Agency (USEPA). These standards outline noise ranges of typical construction equipment that can be found at various types of construction sites.

FHWA Highway Traffic Noise Prediction Model FHWA-RD-77-108
For small-scale projects, CAJA utilizes the Federal Highway Administration (FHWA) Highway Traffic Noise Prediction Model (FHWA-RD-77-108). The FHWA Model is the analytical method presently favored for traffic noise prediction by most State and local agencies, including Caltrans. The FHWA Model predicts hourly Leq values for free-flowing traffic conditions and is generally considered to be accurate within 1.5 decibels (dB).

Transportation Noise Model (TNM Version 2.5)
The FHWA TNM is a state-of-the-art computer program used for predicting noise impacts in the vicinity of highways. It uses advances in computer hardware and software to improve upon the accuracy and ease of modeling highway noise, and is capable of designing effective, cost-efficient highway noise barriers. As of October 14, 2004, the FHWA requires TNM 2.5 to be used for all new traffic noise analyses for federal-aid highway projects.

Typical Construction Noise Generation