The IQOE addressed its five fundamental questions within four themes:

1. The Ocean Soundscapes theme described ocean soundscapes from regional to global scales. This theme included the identification of the primary sound sources and how they contribute to the components of the soundscape, empirical modeling of components of each soundscape, the modeling of acoustic propagation, and the validation of these models using ocean observation systems. This theme was the main focus of efforts to measure trends in ocean sound levels and to define sound budgets within regions. It also investigated soundscape diversity and examined the concept that the conservation of soundscapes may be an appropriate objective for the integrated management of the marine environment.

2. The Effects of Sound on Marine Organisms theme was intended to plan and carry out experiments, including experiments to make regions quieter and to observe the responses of marine organisms to quieting. This theme was intended to include the use of planned experiments as well as opportunistic studies using post-hoc statistical modeling to test for effects. This theme was the main vehicle through which the biological significance of sound would be assessed and, where possible, this would be focused on estimating dose-response relationships so that assessments of the effects of sound can be predictive, with special emphasis on the Population Consequences of Acoustic Disturbance (PCAD) approach. IQOE was unable to make much progress on this theme, due to a lack of dedicated research funding, but the IQOE community was active in studying the effects of changes in human activities due to the COVID-19 pandemic as an opportunistic study.

3. The Observing Sound in the Ocean theme was primarily focused on attempting to add sound measurements to existing and future observing systems and encouraged technical innovation in the measurement of sound. This theme developed data standards—where these do not already exist—and promoted observation of the key biological and physical variables. The IQOE development of a new low-cost open-source sound observing system fit within this theme, as well as development of the MANTA software to standardize processing of acoustic data.

4. The Industry and Regulation theme was intended to develop the methodology for “noise” monitoring within regulatory regimes. This theme was to examine the operational management of sound in the ocean through risk analysis by, among other approaches, defining appropriate thresholds for disturbance, damage to marine life, and harm to marine ecosystems. It was also intended to help regulators to measure compliance, and industry to maintain its activities, by providing innovative solutions to barriers presented by regulation. Because of the lack of research funding, no progress was made by IQOE on this theme.