Less technically, the retroflex consonant [ʂ] sounds somewhat like a mixture between the regular English [ʃ] of "ship" and the "h" at the beginning of "heard", especially when it is pronounced forcefully and with a strong American "r".
The upward curvature of the tongue tip to make apical or subapical contact renders palatalization more difficult so domed (palato-alveolar) consonants are not attested with subapical articulation and fully palatalized (such as alveolo-palatal) sounds occur only with laminal articulation.
Also, the apical-laminal distinction among palato-alveolar sounds makes little (although presumably non-zero[2]) perceptible difference; both articulations, in fact, occur among English-speakers.
[3][page needed] As a result, the differing points of tongue contact (laminal, apical and subapical) are significant largely for retroflex sounds.
There is an additional distinction that can be made among tongue-down laminal sounds, depending on exactly where behind the lower teeth the tongue tip is placed.
Generally, the tongue-down postalveolar consonants have the tongue tip on the hollowed area (with a sublingual cavity), whereas for the tongue-down alveolar consonants, the tongue tip rests against the teeth (no sublingual cavity), which accentuates the hissing vs. hushing distinction of these sounds.
However, the palato-alveolar sibilants in Northwest Caucasian languages such as the extinct Ubykh have the tongue tip resting directly against the lower teeth rather than in the hollowed area.
More common are languages such as Mandarin Chinese and Polish, which distinguish two postalveolar sibilants, typically /ʂ/ /ɕ/ since they are maximally distinct.
Also, Peter Ladefoged, whose notation is used here, has resurrected an obsolete IPA symbol, the under dot, to indicate the apical postalveolar, which is normally included in the category of retroflex consonants.
The notation s̠, ṣ is sometimes reversed, and either may also be called 'retroflex' and written ʂ. Non-sibilant sounds can also be made in the postalveolar region, the number of acoustically distinct variations is then significantly reduced.
The sounds are fairly rare in European languages but occur, for example, in Swedish; they are then often considered to be allophones of sequences such as /rn/ or /rt/.
Also, for some languages that distinguish "dental" vs. "alveolar" stops and nasals, they are actually articulated nearer to prealveolar and postalveolar, respectively.