Vowel sounds provide speech ___________ have acoustic energy concentrated in the _________ frequencies whereas the consonants provide speech ____________ with their energy mainly in the ____________ frequencies.

Vowel sounds are crucial in speech perception because they carry significant acoustic energy, primarily concentrated in the low frequencies. This low-frequency energy helps convey the loudness of speech, allowing listeners to perceive vocal intensity more effectively. In contrast, consonants play a vital role in the intelligibility of speech, as they provide the information necessary for understanding spoken language. The energy from consonants is predominantly found in the high frequencies, which are essential for distinguishing between different consonant sounds.

The first part of the statement emphasizes the low-frequency characteristics of vowel sounds, which indeed contribute to the perception of loudness. The second part highlights that consonants, with their high-frequency energy, are fundamental for understanding speech. This alignment of vowel and consonant characteristics corresponds well with the understanding of speech acoustics and is reflected in the correct answer.