How to Enhance Speech Intelligibility in Presentations
We often discuss sound quality enhancement in music, but for audio processing systems, enhancing speech quality during presentations is also one of its primary functions. However, simply increasing the speaker volume is far from sufficient; maintaining speech intelligibility is equally crucial. Below, we outline factors that affect speech intelligibility.
First, we discuss the fundamental characteristics of sound. Human speech occupies a frequency band with a fundamental frequency ranging from 100-400Hz, averaging around 100Hz for men and 200Hz for women. Within integer multiples of these fundamental frequencies, variations called "formants" occur, producing vowel-like sounds. Impulsive harmonics typically occur between 2kHz and 9kHz. Therefore, processing the entire frequency band is unnecessary; focusing on specific bands suffices to enhance speech clarity. For instance, telephony processes only 300Hz to 3kHz. In noisy environments like factories, reinforcement systems often process the 1kHz to 4kHz range because most speech energy concentrates there.
Additionally, three key factors influence speech intelligibility:
1. Noise Floor: Ideally, the noise floor should be about 25dB below the nominal speech level. If ambient noise is around 15dB and below the speech level, listeners can generally comprehend speech correctly, although they might complain about the noise. However, if the speech-to-noise ratio decreases significantly, listeners struggle to capture the speaker's voice. Audio system processing can then improve intelligibility.
2. Overall SPL (Sound Pressure Level): Generally, there is an upper limit to speech level increase. Face-to-face conversation occurs around 60-65dB, but most reinforcement systems operate in the 70-75dB range. Amplifying the speaker beyond 85dB or 90dB slightly improves intelligibility at best; conversely, listeners complain about excessive volume. Even at high levels, clarity doesn't markedly increase, while most listeners feel oppressed by the loudness.
3. EQ (Equalization): Simple equalization can significantly enhance presenter speech clarity. First, apply a high-pass filter below 80-100Hz to reduce boomy or rumbling sounds. If the speaker has excessive nasal resonance or breathiness, attenuate around 500-800Hz. Conversely, for overly muffled or sibilant ('s', 'sh') voices, apply a boost around 10kHz. For excessively thin voices, boost around 100Hz (men) or 200Hz (women).
First, we discuss the fundamental characteristics of sound. Human speech occupies a frequency band with a fundamental frequency ranging from 100-400Hz, averaging around 100Hz for men and 200Hz for women. Within integer multiples of these fundamental frequencies, variations called "formants" occur, producing vowel-like sounds. Impulsive harmonics typically occur between 2kHz and 9kHz. Therefore, processing the entire frequency band is unnecessary; focusing on specific bands suffices to enhance speech clarity. For instance, telephony processes only 300Hz to 3kHz. In noisy environments like factories, reinforcement systems often process the 1kHz to 4kHz range because most speech energy concentrates there.
Additionally, three key factors influence speech intelligibility:
1. Noise Floor: Ideally, the noise floor should be about 25dB below the nominal speech level. If ambient noise is around 15dB and below the speech level, listeners can generally comprehend speech correctly, although they might complain about the noise. However, if the speech-to-noise ratio decreases significantly, listeners struggle to capture the speaker's voice. Audio system processing can then improve intelligibility.
2. Overall SPL (Sound Pressure Level): Generally, there is an upper limit to speech level increase. Face-to-face conversation occurs around 60-65dB, but most reinforcement systems operate in the 70-75dB range. Amplifying the speaker beyond 85dB or 90dB slightly improves intelligibility at best; conversely, listeners complain about excessive volume. Even at high levels, clarity doesn't markedly increase, while most listeners feel oppressed by the loudness.
3. EQ (Equalization): Simple equalization can significantly enhance presenter speech clarity. First, apply a high-pass filter below 80-100Hz to reduce boomy or rumbling sounds. If the speaker has excessive nasal resonance or breathiness, attenuate around 500-800Hz. Conversely, for overly muffled or sibilant ('s', 'sh') voices, apply a boost around 10kHz. For excessively thin voices, boost around 100Hz (men) or 200Hz (women).