Postvocalic [ɹ] is an interesting sound in the English language. It has often been described as a glide, but I would argue that it is actually more of an off-glide to the preceding vowel. To understand this, let’s break down the articulation of [ɹ] and examine its characteristics.
Firstly, it is important to note that [ɹ] is a voiced sound, meaning the vocal cords vibrate during its production. The primary constriction target for [ɹ] is in the palatal region, specifically the area behind the alveolar ridge. This is where the tongue comes into contact with the roof of the mouth, creating a narrow passage for the airflow.
Unlike other rhotic sounds in different languages, such as the trilled [r] in Spanish or the retroflex [ɻ] in some American English dialects, [ɹ] does not involve any significant lip rounding. This lack of lip involvement is one of the factors that differentiate [ɹ] from a traditional “r” sound.
When producing [ɹ], the tongue is raised towards the roof of the mouth, but it does not create a complete closure, as in the case of stop sounds like [t] or [k]. Instead, there is a small gap between the tongue and the roof of the mouth, allowing the airflow to pass through. This is why [ɹ] is often described as a fricative sound.
However, it is important to note that the tongue movement for [ɹ] is quite different from other fricatives like [s] or [f]. Instead of a continuous and steady airflow, there is a brief constriction followed by a release. This release creates the characteristic off-glide that is associated with [ɹ]. It is this off-glide that gives [ɹ] its distinct quality and sets it apart from other sounds in the English phonetic inventory.
So, to summarize, while [ɹ] is often referred to as a glide, it is more accurately described as an off-glide to the preceding vowel. Its primary constriction target is in the palatal region, with little or no lip rounding. The off-glide is created by a brief constriction followed by a release of the airflow. This unique articulation sets [ɹ] apart from other sounds in the English language.
I hope this explanation helps clarify the nature of [ɹ]. If you have any further questions or need additional clarification, please feel free to ask.