## 3 Spatial Audio Reproduction Techniques for Soundscape Design
### Comparison of Different Spatial Audio Reproduction Techniques for Soundscape Studies  
It is crucial that soundscape researchers select the appropriate sound reproduction technique for their use to make sure that the playback sounds similar to the natural listening scenario. To this end, Table 2 highlights the strengths and weaknesses of common reproduction techniques mentioned above, extended from studies in [80].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Reproduction Techniques** & **Number of Channels** & **Strengths** & **Weaknesses** \\ \hline \hline \multirow{4}{*}{Binaural} & \multirow{4}{*}{Two} & \(\bullet\) & Enables creation of virtual source in 3D space with two channels. & \(\bullet\) & It is only suitable for single user. \\  & & \(\bullet\) & Lower equipment cost as compared to other solutions. & \(\bullet\) & Individualized HRTFs needed to avoid front back confusions and in-head localizations. \\ \hline \multirow{4}{*}{Transaural} & \multirow{4}{*}{Two or four} & \(\bullet\) & Enhances spaciousness and realism of audio with limited number of speakers. & \(\bullet\) & Requires effective crosstalk cancellation. \\  & & \(\bullet\) & Accurate rendering of spatial images using fewer loudspeakers. & \(\bullet\) & It is only suitable for single user. \\ \hline \hline \multirow{4}{*}{Stereo} & \multirow{4}{*}{Two} & \multirow{4}{*}{Legacy reproduction method. Widely adopted in industry.} & \(\bullet\) & Poor spatial effect. \\  & & \(\bullet\) & Better spaciousness of 360\({}^{\circ}\) audio as compared to stereo setups. & \(\bullet\) & The sound phantom image is always created at sweet spot. \\ \cline{1-1} \cline{3-4}  & & \(\bullet\) & Better spaciousness of 360\({}^{\circ}\) audio as compared to stereo setups. & \(\bullet\) & Large numbers of channels and speaker systems needed for spatial realism. \\ \cline{1-1} \cline{3-4}  & & \(\bullet\) & Well adopted by industry. & \(\bullet\) & Unable to achieve accurate 360 degree phantom images. \\ \hline \multirow{4}{*}{Ambisonics} & \multirow{4}{*}{(N + 1)\({}^{2}\) for Nth Ambisonic} & \(\bullet\) & Can be used with any speaker arrangement. & \(\bullet\) & Listener movement can cause artifacts in sound. \\  & & \(\bullet\) & Core technology is not patented and free to use. & \(\bullet\) & Complicated setup. \\ \hline \multirow{4}{*}{Wave Field Synthesis} & \multirow{4}{*}{More than 100 usually} & \(\bullet\) & The sweet spot covers entire listening area. & \(\bullet\) & High frequency sounds beyond \\  & & \(\bullet\) & The virtual sound sources & & allsing frequency not well reproduced. \\ \cline{1-1} \cline{3-4}  & & \(\bullet\) & Independent of listener position & \(\bullet\) & Large number of speakers needed. \\ \hline \hline \end{tabular}
\end{table}
Table 2: Strengths and weaknesses of reproduction techniques for soundscape studies.  
In addition to the above techniques, Auralization techniques have recently become popular among soundscape researchers to achieve sufficient perceptual accuracy of acoustic reproduction. Auralization can be defined as a technique of creating audible sound files from numerical data [81]. It is not strictly a perceptual technique and can include the physical reproduction methods as well. The technique has been used in reproducing various acoustic environments, such as concert halls [82], auditoriums [83] and in room acoustics. The development of accurate models and efficient algorithms for accurate sound reproduction employs various techniques, like ray tracing [84], radiosity methods [85], finite element methods, etc. [86]. These models are used in conjugation with the reproduction setups to add audio effects and cues for increasing realism and spaciousness for spatial sound.