Which frequency range is most associated with difficult speech levels?

In the context of speech intelligibility and the frequencies that are critical for understanding spoken communication, the range of 500-2000 Hz is particularly significant. This range encompasses the fundamental frequencies of human speech and the harmonics that contribute most to clarity and recognition of phonetic sounds.

Sounds within this frequency range contain the essential components for speech discrimination, such as consonants and vowel sounds, which are crucial for comprehension. It is within these frequencies that many of the important acoustic cues reside, which are needed to grasp the nuances of speech, especially in noisy environments where understanding becomes more challenging.

While higher frequencies can also contribute to speech intelligibility, particularly consonant sounds, the 500-2000 Hz range is where the majority of speech intelligibility occurs. Hence, this frequency range is associated with difficult speech levels, especially in environments with background noise or other auditory distractions that can obscure these key frequencies.