## 3 Spatial Audio Reproduction Techniques for Soundscape Design  
Perceptually accurate reproduction of the acoustic environment is crucial to achieve high ecological validity for evaluation of soundscape in laboratory conditions. This requires synthesis and rendering of different sound sources to create an immersive playback system, for instance, in subjective listening tests with sufficient perceptual accuracy. Soundscape composition and acoustic reproduction was pioneered by [PERSON] and his group in 1970s when they published a record titled \"The Vancouver soundscape\" [PERSON] (1970). As the reproduction techniques for spatial audio become more advanced, the soundscape researchers started adopting them in their studies from stereophonic techniques, multi-channel setups [PERSON] (1970), to ambisonics and wave field synthesis [PERSON] (1970). A rendering algorithm along with multiple transducers are often used for reproduction of spatial sound. The sound can be rendered using either a pair of headphones or an array of loudspeakers arranged in a specific configuration. The aim of the system is to reproduce the sound field in such a \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Recording Techniques** & & **Strengths** & **Weaknesses** & **Remarks** \\ \hline \multirow{4}{*}{Stereo and Surround recording} & \(\bullet\) & Legacy recording methods; & \(\bullet\) & Does not capture 3D sound field (usually only covers 1D or 2D); & \\  & \(\bullet\) & Widely adopted in industry; & \(\bullet\) & Not suitable for direct playback & \(\bullet\) & Limited spatial quality in soundscape studies. \\  & \(\bullet\) & Direct playback over loudspeaker system. & \(\bullet\) & Does not support & \\  & & & head movements. & & \\ \hline \multirow{4}{*}{Microphone arrays} & \(\bullet\) & Ability to focus on certain sounds in different sound fields; & \(\bullet\) & Requires large number of microphones for good performance; & \(\bullet\) & A general method that could be used to record a more complete sound field for \\  & \(\bullet\) & Support head movements. & \(\bullet\) & Requires sophisticated signal processing to obtain desired & \(\bullet\) & soundscape reproduction. \\  & \(\bullet\) & & & sound from recording. & \\ \hline \multirow{4}{*}{Ambisonics} & \(\bullet\) & Records 3D sound fields with only 4 microphones; & \(\bullet\) & Not suitable for non-digetic & \\  & & Good mathematical foundations for recording and playback; & \(\bullet\) & Sentler performance requires higher order ambisonics; & \(\bullet\) & Well suited for interactive reproduction in soundscape studies. \\  & \(\bullet\) & Efficient rendering for interactive applications; & \(\bullet\) & Absence of international standards. & \\  & \(\bullet\) & Rapidly increasing popularity in industry. & & & \\ \hline \multirow{4}{*}{Binaural recordings} & \(\bullet\) & Closest to human hearing; & \(\bullet\) & Specialized equipment needed, \(\bullet\) & Most commonly used recording technique for soundscape studies due to its simplicity; \\  & \(\bullet\) & Direct playback over headphones. & \(\bullet\) & Delect of support for head movements; & \(\bullet\) & Good spatial quality but limited interaction in soundscape studies \\ \cline{1-1}  & & & & Non-personalized rendering (e.g., dummy head recordings). & \(\bullet\) & Personalized rendering (i.e., from in-ear binaural microphones). \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of recording techniques for soundscape studies. manner so as to give a sense of perception of spaciousness and directivity of sound objects located in 3D space [27]. The sounds generated in such a scenario are often referred to as virtual sound in contrast to real sound we commonly hear in everyday life [59]. The earliest attempt for reproduction of sound dates back to the phonograph invented in 1887. The first stereo system was introduced by Bluemin [60] in 1931 with its first commercial use in 1949. Dolby introduced the first surround sound system in 1970 and in the same year, Gerzon invented ambisonics [49].