# Design and Evaluation of a Web- and Mobile-Based Binaural Audio Platform for Cultural Heritage
## 2 Background  
### Sonic Narratives and Web-Based Spatial Audio  
A sonic narrative is defined as a sequence of sounds that suggests a sense of causality and temporal evolution. This is usually achieved through the interplay of tension and resolution in the acoustic properties of the sequence, or through its referential qualities [13]. Generally based on music features (e.g., timbre, pitch-melody, tempo, etc.) [14], sonic narratives are often not interactive (i.e., simple audio playback). Conversely, a soundscape is defined as the sum of natural, animal and human sounds that describe a landscape or environment [15] and--while dynamic at the single acoustic events level--it typically describes a static scene, with no control over the listening or sound sources' position and/or proximity.  
The aim of binaural spatialisation is to provide the listener (through standard headphones) with the impression that sound is positioned in a specific location in the three-dimensional space. The 3D characteristics of the sound can be captured during recording with special hardware, or simulated in post-production via spatialisation techniques. The addition of spatial attributes (e.g., placement of sound sources on a full 360 deg sphere, and at different distances), and most of all the addition of interactivity (e.g., to navigate soundscapes or sonic narratives moving around in the acoustic virtual environment), are features which have not been widely explored until now within the context of digital heritage. For example, the authors of [16] explored spatial sonic narratives, but exploited simple 2-dimensional audio panning techniques.  
The theories at the basis of the binaural spatialisation technique are not particularly recent, and the first binaural recording dates back to the end of the 19 th Century [17]. However, it is only within the last twenty years that the increase in the calculation power of personal computers enabled an accurate real-time simulation of three-dimensional sound-fields over headphones.  
With the release of the Web Audio (WAA) [18] and the Web GL (WGL) [19] APIs in 2011, and with the specification of HTML5 in 2014, the World Wide Web Consortium (W3C) and Mozilla Foundation set the basis for the development of modern web applications. As stated in the introduction to the WAA [20], the specification of a high-level Javascript (JS) API was necessary to satisfy the demand for audio and video processing capabilities that would allow to develop \"sophisticated web-based games or interactive applications\". To obtain performances comparable to modern digital audio workstations (DAWs) and games graphical engines, the two organisations decided to move the burden of audio and video processing from the server to the client (i.e., browser) side.  
Several tools currently exist that perform binaural spatialisation, just to mention a few: Anaglyph [21], IRCAM Spat [22], the IEM binaural audio open library [23] and the 3D Tune-In Toolkit [24]. Although, very few of these are designed for non-expert users or implemented within a web-based application, and therefore available on multiple platformsthrough a simple browser. The idea of developing and evaluating web and mobile applications for the creation and experience of 3D sonic narratives and soundscapes does indeed represent a novel contribution to both the digital heritage and audio technology domains.