Autism spectrum disorders (ASD) are defined in terms of qualitative atypicalities in social communication and interaction in the presence of restricted, repetitive patterns of behaviour, interests and activities (RRBs). Part of the main criteria for RRBs is hyper/hypo reactivity to sensory input, which appear to be particularly prevalent in the auditory domain and could result in atypical behaviours (APA, 2013). Despite the crucial role that sensory processing plays in learning, attention, cognitive and brain maturation, emotional regulation, and social communication development in humans (e.g., Ahn et al., 2004; Bundy et al., 2007), it remains unclear what precisely causes the sensory atypicalities observed in ASD or how they are associated with the development of key autistic symptomatology such as impairments in social communication (e.g., Jones et al., 2009; Leekam Prior & Uljarević, 2011). Thus, the main aim of the present thesis is to explore the nature of the auditory sensory issues and their relationship with core symptoms (i.e., RRBs and communicative ability) in ASD and the broader autism phenotype (BAP). In addition, the associations among speech perception and production, and communication were investigated. Four studies were conducted using adult samples with and without ASD. Chapter 2 reports findings indicating that the perception of intensity and frequency auditory parameters influence the severity of RRBs and that primary auditory discrimination abilities are characterised by high variability in ASD. Chapters 3 & 4 present evidence showing that the relationship between auditory intensity perception and sensation avoiding behaviours contribute to the communicative difficulties observed in adults with ASD or high levels of autistic traits. Chapter 5 provides a direct demonstration of deficits on primary syllable stress perception in ASD and its role on the speech production abnormalities and socio-communicative atypicalities in ASD. Taken together, the outcome of these investigations highlights the importance of considering the development of core autistic symptoms as an interactional multi-developmental process, which extends into the general population.