I am not an English student, by discipline I am physicist, so am asking this question in innocence.
I searched Google for the longest word without a vowel sound and I get these results:
The longest common word without any of the five vowels is RHYTHMS, but there are longer rare words: SYMPHYSY, NYMPHLY, GYPSYRY, GYPSYFY
However, English student don't agree, they say there is an
\schwa\ in the word RHYTHM.
I am confused, what should I believe, the internet or my English university students?