In order to promote the enhancement of indoor acoustic quality in public places, the Environmental Protection Administration (EPA) of the Executive Yuan has required the management unit of various public places to manage the indoor acoustic quality in an autonomous manner. Since 2007 and 2008, researches on indoor noise level in public places, such as libraries, hospitals and depots/stations/offices of the ground transportation system, have been conducted one after another. Starting from 2007, researches on indoor acoustic quality in residential areas have been added to these efforts, and the recommended indicators and permissible noise levels for indoor sound level adopted by various countries were referenced for the purpose of maintaining citizens’ health and environmental tranquility in order to enhance the quality of life of our compatriots. Although the measurement of indoor/outdoor acoustic quality in residential areas conducted in this project belongs to the work of EPA’s technology research projects, since the building indoor noise is the responsibility of the Construction and Planning Agency of the Ministry of the Interior, instead of EPA, the purpose of measurement concerning this project is not to propose indoor noise control standards, but to understand and find out whether or not there is room for improvement of current noise control standards at the source end so as to understand and improve the indoor acoustic environmental quality. The achievements of this research project include:
1. Completed collecting, organizing and analyzing papers relating to the establishment and application status of environmental noise assessment indicators adopted in foreign countries.
1) Completed collecting and organizing 10 papers relating to the establishment and application status of environmental noise assessment indicators adopted in foreign countries, hence found out that equivalent sound level LAeq was commonly used as an assessment indicator for environmental noise in foreign countries.
2) Completed collecting and organizing papers relating to the establishment methods of environmental noise assessment indicators adopted in foreign countries, hence found out that the community survey and objective measurement were commonly used to establish environmental noise assessment indicators in foreign countries and four methods were most commonly used to establish noise assessment and prediction – empirical formula, analysis model, computer model, and model experiment. The findings might serve as a reference for the future establishment of noise assessment indicators and methods in our country.
2. Completed collecting indoor noise quality indicators, noise measurements, recommended exposure limits, and noise assessment/simulation methods adopted for residential areas in foreign countries.
1) Completed collecting research results relating to the noise status and noise annoyance level perceived by the public in residential areas in foreign countries.
Completed collecting and analyzing related data on the noise status in residential areas in 6 countries or districts, including South Korea, China, Hong Kong, Japan, the EU, and the US, hence found out that middle and low frequency noises were getting more and more attention and, according to the research in foreign countries, if A-weighting was used, compensation should be applied in order to reflect the noise annoyance caused by the low frequency noise in residential areas in a more objective manner.
2) Completed collecting and analyzing the noise related indicators, standards or recommended exposure limits for residential areas in different countries.
Completed collecting and analyzing the indoor noise quality assessment indicators adopted in 16 foreign residential areas, hence found out that LAeq was used as the sole noise assessment indicator in most residential areas with only the World Health Organization (WHO), Manchester (UK), and Korea also adopting LAmax as an extra assessment indicator. The findings might serve as a reference for the future establishment of indoor noise assessment indicators for residential areas in our country.
3) Completed collecting and analyzing the measurement methods and SOPs for indoor noise assessment in residential areas in foreign countries and making reference of EPA’s research projects concerning the “indoor noise level in public places, such libraries and hospitals” (2007, 2008) and “indoor noise level at stations of ground transportation systems” (2009, 2012). The findings might serve as a reference for formulating recommended exposure limits and measurement methods of indoor noise in the future in our country.
4) Completed collecting the indoor noise assessment and simulation methods adopted in five countries, including Denmark, Belgium, New Zealand, Germany, and Japan, as well as introducing Japan’s empirical formula and computing concepts for indoor noise assessment.
3. Completed investigating the sound level and distribution of noise sources in indoor/outdoor places in residential areas, as well as conducting related research on the improvement of measurement methods of sound insulation in buildings and acoustic structures.
1) Completed research on indoor/outdoor noise measurement in residential areas.
According to the contract, 10 point-times of noise level measurement at indoor/outdoor places in residential areas should be conducted. In this project, our project team conducted 20 point-times of measurement in total, including 1 point-time on the normal road, 9 point-times on the road system (freeway and expressway), and 10 point-times on the rail system (MRT, TRA, and THSR), with various conditions and situations considered, such as open window, closed window, reflected sound, and acoustic attenuation.
In this project, the Leq of open/closed window field measurements is similar to that contained in foreign papers. The average of sound reduction in closed-window condition is preliminarily estimated to be around 20 dB, and in open-window condition, around 10 dB. As shown in the table, in open-window condition, with an indoor/outdoor gap of 10 dB (acoustic attenuation), there is room for improvement of 10-15 dB comparing to the indoor recommended exposure limits and noise control standards for ground transportation systems in our country. The noise control measures can be made either on the noise source end or the receiving end. In the case of closed window condition, the indoor noise level is close to the indoor recommended exposure limits.
2) Completed survey and analysis of indoor noise source distribution and spectral data.
As shown by the survey and analysis of indoor noise source distribution and spectral data, on the part of frequency lower than 200Hz, the linear change of indoor/outdoor sound levels is obvious, indicating that there is interference of low frequency noise sound indoors.
3) Analyzed the test principles and conditions of measurement methods of sound insulation in buildings, conducted noise source tests, and proposed recommendations for improvement of measurement methods of sound insulation in buildings.
Our project team completed pros and cons comparison of 3 measurement methods, including lab measurement method, field measurement method (on traffic noise source), and field measurement method (on speaker noise source). When conducting sound insulation field measurement or acceptance on speaker noise source, it is okay to just measure the sound insulation of a 45。 incident member in order to reduce the workload of measurement or acceptance.
4) Conducted theory research and experiment analysis on thin/light sound insulation structures and theoretical analysis and experiment on at least two types of soundproof structural performances.
Our project team conducted three kinds of soundproof structural analysis. The analytical results show that various soundproof materials perform better on middle to high frequency noise than low frequency noise.
4. Completed researching and proposing the indoor noise quality indicators, measurement methods, and recommended exposure limits in residential areas in our country and held explanation and consulting meetings to collect opinions from all circles.
1) Held an explanation meeting at the 2nd meeting room of Taipei Railway Station on June 20, 2017 to explain and discuss topics concerning field measurement operational planning, such as indoor noise quality indicators in residential areas, indoor/outdoor measurement methods, quantity allocation, noise source distribution, and spectral data survey/analysis.
2) Held an academics and experts consulting meeting at the 6th meeting room of Dharma Drum Degui Academy on August 28, 2017 to discuss, explain, and exchange views on the preliminary results of field measurement on topics such as indoor noise quality indicators in residential areas, measurement methods, recommended exposure limits, and indoor/outdoor field measurement operational planning, to provide reference for the EPA.
3) Held a second explanation meeting at the 6th meeting room of Dharma Drum Degui Academy on November 15, 2017 to explain the measurement results at indoor and outdoor places.