Early reflections play a large role in our perception of sound and as such, have been subject to various treatments over the years due to changing tastes and room requirements. Whilst there is research into these early reflections, arriving both vertically and horizontally in small rooms regarding critical listening, little research has been conducted regarding the beneficial or detrimental impact of early vertical reflections on listener preference, in the context of listening for entertainment. Two experiments were conducted through subjective testing in a semi-anechoic chamber and listening room in order to assess subjects’ preference of playback of a direct sound against playback with the addition of the first geometrical vertical reflection. Program material remained constant in both experiments, employing five musical and one speech stimuli. The first experiment used a paired comparison method assessing a subjects’ preference, and perceived magnitude of timbral and spatial difference provided by a frequency independent ceiling reflection. Each comparison was followed by a free verbalisation task for subjects to describe the perceived change(s). The second experiment investigated this further by focusing specifically on subjects’ preference with a frequency dependent reflection. A more controlled verbalisation task provided a list of descriptive terms which the subject’s used to describe which attribute(s) influenced their preference. The results show that preference for playback with the inclusion of a vertical reflection was highly varied across both subjects and samples. However both experiments suggest that the main perceptual attribute with which subject’s based their preference was timbre, common spatial attributes (image shift/spread) cannot be used to predict preference. Experiment two suggests that the alteration of the frequency content of a vertical reflection, may also provide a more consistent level of preference for certain stimuli. It is also shown that while certain attributes occur frequently (brilliance/fullness) for describing preference, others less frequently used (nasal/boxy), may influence preference to a greater extent.

Masters by Research project, 2015 – 2016

Researcher: Tom Robotham

Supervisors: Dr Matthew Stephenson, Dr Hyunkook Lee

Publications:

• Robotham, T., Stephenson, M., & Lee, H. (2016). The effect of a vertical reflection on the relationship between preference and perceived change in timbral and spatial attributes. In 140th Audio Engineering Society International Convention 2016, AES 2016 [9547] Audio Engineering Society.