## 2 Spatial Audio Recording Techniques for Soundscape Design
### Application of Spatial Audio Recording in Soundscape Studies  
The section discusses how we can adopt different recordings techniques for soundscape studies. As the application of soundscape is relatively new, there are no comprehensive standards in terms of how recordings should be conducted for studies or reports on soundscape. Soundscape researchers employ different recording techniques for capturing the acoustic environment depending on various factors, such as the fidelity of reproduction medium, ease of capture, cost, etc.  
Binaural and ambisonics are the two most common recording techniques in soundscape studies. Many have used binaural measurement systems, such as an artificial head or binaural microphones to record acoustic environment and binaural recordings are used for the reproduction of acoustic environments in laboratory-based listening experiments [54; 55; 56]. Ambisonic recording methods have recently received much attention in soundscape studies, as they are not restricted by playback mediums. [PERSON] et al. [28] captured the acoustic environment in different parts of New York with an ambisonic microphone. [PERSON] et al. [22] also used a FOA ambisonics microphone to record urban areas in Manchester, UK.  
Although the mentioned recording methods for soundscape applications are not extensive, some insights can be gained to better understand how different recording techniques can be used in soundscape studies. Let us consider the three stages of the soundscape design process as introduced in Section 1. In Stage 1, recordings are used to evaluate the existing soundscape. In Stage 2, recordings are used to design a better soundscape. Finally, recordings are captured to validate the design soundscape after its implementation. In all these stages, the most critical requirement for soundscape recording is that it must sufficiently represent the characteristics of the acoustic environment in question that would facilitate the reproduction of the acoustic environment with sufficient perceptual accuracy. It should be made clear that the degree of perceptual accuracy is dependent on the goal of the study. On this note, the recording techniques must also be chosen with consideration of the reproduction mediums. A detailed review of the spatial audio reproduction techniques can be found in Section 3.  
While the community continues to develop recording techniques for spatial audio reproduction, there are some trends and early examples that we can learn from. The strengths and weaknesses of these recording techniques in terms of their applications in soundscape studies are summarized in Table 1. With its simplicity, it is evident that ambisonics is the leading recording technique  
Figure 6: Ambisonics microphones (from left to right): Sennheiser AMBEO, Core Sound TetraMic, and SoundField SPS200.  
for interactive spatial audio reproduction. On the other hand, conventional stereo and surround recording techniques can still be employed for specific applications, such as non-digeetic sound (or ambience) of the acoustic environment in soundscape studies. Microphone arrays are very useful to capture a more complete sound field (depending on the number of microphones used) and could be used in postprocessing to further emphasize certain sound components, such as, speech from noisy environment. Binaural recording still works great with static listening positions, but it does not allow interactions in soundscape studies. Even monophonic microphones are required for dry recordings that can be spatialized with post-processing, such as in auralization. Thus, it is clear that choosing the most suitable recording techniques depends on the reproduction techniques as well as the degree of perceptual accuracy required for soundscape studies. For high degree of perceptual accuracy, interactive spatial audio reproduction is required, and thus, ambisonic recordings might be a more suitable choice.