• Parasagittal tongue sensor positions alone unreliably measure lateralization. • Lateralization is reliably quantified using EMA with 3D palate shape data. • Tongue-side lowering relative to the palate distinguishes /l/ from /t/ and /n/. • Taiwanese Mandarin /l/ does not show greater lateral asymmetry than /t/ or /n/. • Lateral tongue bracing before /l/ release is vowel-dependent, occurring only in /i/. This study uses electromagnetic articulography to examine the articulation of three coronal sounds in Taiwanese Mandarin: /l/, /t/, and /n/. Two methods are employed to analyze their lateral kinematics. The first compares the positions of parasagittal sensors with those of midsagittal sensors, quantifying lateralization based on their relative positions, with laterals expected to be produced with lowered sides of the tongue. The second compares the positions of the parasagittal sensors against the position of an estimated three-dimensional palate surface model of the speaker. Results from the first method indicated that lateral consonants do not necessarily involve lowering of the sides of the tongue relative to the midsagittal position. Results from the second method indicated that a significantly larger opening is measured between the parasagittal sensors and the palate for the lateral /l/ when compared to /t/ and /n/. Together, the results indicate that including the position of the palate is critical when quantifying lateralization. Coarticulatory effects of the following vowel were also more clearly interpreted from the second method, with the high-front vowel /i/ triggering lateral tongue bracing prior to the release of /l/. These findings demonstrate that incorporating palate morphology is essential for accurately capturing lateral articulation and associated coarticulatory patterns.

• Vowels and stops are more rate-sensitive than fricatives and nasals in Japanese production. • These patterns align well with the observed ratios of geminate to singleton consonants. • Perception results broadly mirror the production patterns. This study examines the sensitivity of vowels and consonants to speaking rate variations in both production and perception, using Japanese as a case study. In contrast to prior studies, which suggest that vowels are more responsive to speaking rate changes than consonants in production, our results indicate a more nuanced distinction between vowels and stops versus fricatives and nasals, with the former group exhibiting greater sensitivity to speaking rate changes. Furthermore, this production pattern was also generally reflected, though to a lesser extent, in the perception results. These findings point to the need for further research into factors such as the presence or absence of length distinctions, language-specific prosodic and rhythmic characteristics, and the relationship between the ratios of long to short segments and slow to fast speaking rates.

• Fourteen studies show that fine phonetic detail is systematically regulated in shaping sound systems. • Fine phonetic detail links production, perception, and learning, sustaining contrasts and enabling sound change. • Sound systems emerge from controlled allocation of continuous phonetic parameters within prosodic structure. • Prosodic structure guides segmental and suprasegmental realization across languages and domains. • Phonetic grammar is a language-specific, system-internal control system shaped by motor, perceptual, and cognitive pressures. This special issue examines how fine phonetic detail participates in the shaping of sound systems. Across fourteen studies, the central theme is that subtle temporal, spectral, and articulatory patterns are not incidental by-products of articulation, but are systematically regulated aspects of speakers’ phonetic knowledge. They provide the means through which phonological contrasts and prosodic structure are realized, maintained, and sometimes reorganized. The contributions show how languages allocate continuous phonetic parameters—such as timing, coordination, voice quality, and nasality—within prosodic domains (e.g., phrases, words, and syllables) and under general biomechanical and communicative pressures. Studies of Irish, Hawaiian, Japanese, and Mandarin illustrate how prosodic structure guides segmental and suprasegmental realization. Work on English, German, Danish, and Cantonese demonstrates how fine phonetic detail underlies patterns of variation and creates potential pathways for change. Production connects naturally to perception and learning: findings from English accent adaptation and Samoan iterated learning reveal how listeners stabilize or reinterpret detail, linking individual processing to community-level patterning. A set of studies on Italian, Korean, English, and L2 German show how prominence reorganizes cues across articulation, interaction, and acquisition, shaping how speakers signal and listeners recover linguistic structure. These studies converge on a view in which fine phonetic detail arises from a central phonetic component (or the phonetic grammar) of linguistic structure—controlled by speakers, shaped by universal motor and perceptual constraints, and continually adjusted through perception and learning. In this perspective, sound systems emerge from the interplay of these regulated patterns, which sustain contrasts, support communication, and open principled routes for change.