Background Noise generated by human activities is a considerable environmental problem, especially in urban areas with high populations. In the European Union, nearly 100 million people are exposed to noise levels considered as damaging to their health. In order to address this issue, EC directive 2002/49 requires Member States to develop and publish strategic noise maps using modelling data. Modelling makes it possible to represent noise pollution over a large area at relatively low cost. However, the results may seem distant from people's perceptions of noise pollution. Increased awareness of noise pollution by the general public and the relevant authorities is therefore necessary for improving the effectiveness of policies to reduce environmental noise. Objectives The HARMONICA project aimed to develop and disseminate innovative tools to assist decision-making concerning noise pollution, using an easy-to-understand and common noise index that takes into account people's perception of noise. The project sought to gather as much noise information as possible on a web portal, to provide a harmonised framework for monitoring and evaluating noise pollution. Improved access to information should increase public awareness and assist authorities, while also facilitating the transfer of information between European agglomerations, who, it is hoped, will join the platform in the future. Results The HARMONICA project addressed the need for making noise maps, prepared by Member States under EC Directive 2002/49, easier to understand for the general public and decision-makers. This noise information is published every five years, and includes maps and noise management action plans for major agglomerations, roads, railways and airports. Member States apply the noise indicators Lden and Lnight to prepare and revise the strategic mapping, but these indices are technical and not readily understood by the general public and decision-makers. Therefore, the project defined a new easy-to-understand noise index, which better reflects people's perceptions of noise. The index was formulated through a rigorous scientific protocol and with people's feedback. The innovative features of the index lie in its analysis of noise and its user-friendly graphical representation. The index has no units, but ranks noise perception from 0 to 10, whereas existing indicators use decibels (which is a complex unit, based on a logarithmic scale). The new index takes into account an analysis of the two major components of the noise environment: background noise and peak noise events that exceed this background. It can be calculated simply from data collected by noise measurement devices. The Harmonica index is calculated for one-hour time slots, so it is possible to represent changes over a day and derive average results over any period (e.g. day, night, 24-hours, week, month, or year). This is very useful; for example, making it possible to distinguish between day and night time, as people tend to be more sensitive to noise pollution at night. The graphical representation of the Harmonica index is simple and easy-to-understand, which was confirmed by a survey involving 800 people. The index is represented by a triangle on top of a rectangle, in order to clearly translate its two components, and with colours (green/orange/red) indicating how the noise environment compares to the WHO’s (World Health Organisation) environmental quality objectives and the values recognised as critical for noise. A free software tool called Toots has been made available for users to test the calculation of the index "at home" with their own noise data, and to produce graphical representations of it. The project team produced a short film to accompany the Harmonica index, which explains its features to both professionals and laymen. A 32-page methodological guide was also produced, to help users get acquainted with the new noise index. Innovative web tools were developed to disseminate the use of the Harmonica index and share information on noise abatement operations at the EU level. The dissemination tools comprised a platform displaying the index, a database that gathered together European noise abatement actions (e.g. reduced road speed and new asphalt coatings) for the first time (initially 24 actions with more to be included), and a web portal called NoiseInEu (www.noiseineu.eu) that provides information and support for an expert community network. These outputs provide reliable, clear, and easy-to-understand information on noise pollution to EU citizens and to decision-makers. All the project’s outputs (e.g. tools, database, Toots, film and guides) have been made available to the public and professional users (e.g. local authority decision-makers, private companies, NGOs) via the portal (www.noiseineu.eu). The project also disseminated its results through workshops, a website, the media and a layman’s report. The demonstration of the index, and a common protocol for noise measurement, enabled data collected by different noise monitoring managers to be made available on the same platform for the first time. For the moment, data is displayed for 50 stations managed by project beneficiary Bruitparif and 10 by project partner Acoucité, but other organisations are expected to join the platform. A questionnaire sent to cities around the EU helped identify interested future partners (e.g. Lille, Brussels, Barcelona). The increasing use of the Harmonica index to identify and assess noise abatement actions will help harmonise noise monitoring results across the EU, allow comparison between different regions, ensure monitoring results better reflect how noise is perceived by people, and lead to better access to information on noise exposure. The educational tools to communicate the benefits of noise abatement actions will help promote such policies and raise awareness among the general public and decision-makers. In the long term, the project outcomes should contribute to the development of policies to combat noise pollution and to a better integration of noise issues into territorial policies or programmes at the European, national and local levels. This should lead to a reduction in noise pollution, which currently affects nearly 100 million people in the EU. With numerous scientific studies establishing a link between noise pollution and health problems (e.g. sleep disturbances and stress), the project, by contributing to noise pollution reduction, could help bring about significant socio-economic benefits. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).