Speech Communications Chapter 7 Speech Communications The Nature

Speech Communications Chapter 7

Speech Communications The Nature of Speech Criteria for Evaluating Speech Components of Speech Communication System Synthesized Speech

The Nature of Speech 1/2 發聲: 呼吸系統, Articulators Types of Speech Sound ¡Phoneme (音素) − shortest segment of speech if change → meaning change ¡分類: 母音 (vowel), 子音 (consonant) 雙母音 (diphthongs) ¡Phoneme →Syllable →Word → Sentence

The Nature of Speech 2/2 Depicting Speech ¡Waveform, Spectrum ¡Sound spectrogram Fig 8 -1 Intensity of Speech ¡Average intensity (speech power): 母音＞子音 ¡Intelligibility: 子音較重要 Frequency Composition of Speech ¡低頻: 男＞女 Fig 8 -2 ¡Shouting: frequency上升

Criteria for Evaluating Speech Intelligibility (能解度) ¡方法 − Repeat 呈現的聲音 − 回答問題 ¡Test − Nonsense syllables − Isolated words (phonetically balanced, PB) − Sentences Speech quality (Naturalness) ¡Preference

Components of Speech Communication System Speaker Message Transmission System Noise Hearer

Components of Speech Communication System Speaker ¡Enunciation (清晰的聲音) ¡Superior Speakers − Longer syllable duration − Greater intensity − More total time with speech sounds − Frequencies varied 1/7

Components of Speech Communication System Message ¡Phoneme Confusion − DVPBGCET, FXSH, KJA, MN − Avoid single letters, Word-spelling alphabet ¡Word Characteristics − Familiar words − Long words 2/7

Components of Speech Communication System Message ¡Context Features − Sentence: meaningful＞nonsense − Set size: 字多＜字少 − Guidelines ¡用較少的字 ¡Standard sentence ¡Avoid short word ¡Familiarize user 3/7 Fig 7 -3

Components of Speech Communication System Transmission System ¡Filtering (Frequency distortion) − High-pass: cutoff＜ 600 Hz − Low-pass: cutoff＞ 4000 Hz Fig 7 -4 ¡Amplitude Distortion Fig 7 -5 7 -6 − Peak clipping Quality , Intelligibility ≈ − Center clipping Intelligibility − 提高 Intelligibility: Peak clipping Amplify ( 子音/母音 ) 4/7

Components of Speech Communication System Noise ¡Articulation Index (AI) Fig 7 -7 − 1/3 octave, S-N, weighted sum − Intelligibility Fig 7 -8 Tab 7 -1 ¡Preferred-Octave Speech Interference Level (PSIL) − Mean of 500, 1000, 2000 Hz (octave) − SIL: Mean of 600 -1200, 1200 -2400, . . . − Intelligibility (vs. distance) Fig 7 -9 − Subjective rating Fig 7 -10 Tab 7 -2 5/7

Components of Speech Communication System Noise ¡Preferred Noise Criterion Curve (PNC) Fig 7 -11 Tab 7 -3 ¡Reverberation Fig 7 -12 − Reverberation time: Decay 60 d. B − Reverberation time Intelligibility 6/7

Components of Speech Communication System Hearer ¡Age Fig 7 -13 ¡Wearing of Hearing Protection 7/7

Synthesized Speech 種類 Uses Performance Preference Guidelines

Synthesized Speech 種類 ¡Synthesis by Analysis − Digitized human speech compressed data format − 缺點: 限於 encoded & stored Lack of coarticulation ¡Synthesis by Rule − 缺點: quality 較差