Klaske van Sluis

22 2.2. Materials and methods “speech”, “electrolarynx”, “esophageal”, “tracheoesophageal”, “acoustics”, “intel- ligibility”, “voice quality”, “quality of life” and their synonyms. The criteria for inclusion were that the written language was English, Dutch, German, Span- ish or French. No filter for publication date was applied, and the search was performed in January 2016, with an update in December 2016. Table 2.1: Research questions and outcomes of interest Research questions • Which comparative acoustic, perceptual, and PROs are available for TES, ES and ELS after TL • How do outcomes of TES, ES and ELS relate to those of normal laryngeal speech? • What outcomes are favorable in which rehabilitation method? Primary Outcomes Acoustic F0 : fundamental frequency, a result of the rate of vi- bration of the (neo) glottis [15] HNR : harmonics to noise ratio, ratio between the to- tal energy of the periodic voice signal and the energy of noise components [15, 17, 20] %voiced : the percentage voicedness [9, 16, 17] Perceptual Voice quality : impression of the overall voice quality [8, 9, 14] Intelligibility : impression of the intelligibility [8, 18] PROs VHI : Voice Handicap Index [13] V-RQOL : voice-related quality of life [14] Secondary Outcomes Acoustic Jitter : relative variability in the period-to-period fre- quency [20, 21] Shimmer : relative variability in the peak-to-peak amplitude [20, 21] Intensity : Loudness dB [8, 22] Spectral tilt : a comparison between low frequency energy (between 0 and 1 kHz) and high frequency en- ergy (between 1 and 5 kHz) [21, 23] MPT: Maximum Phonation Time [22, 24] Perceptual GRBAS : Grade Roughness Breathiness Asthenia Strain scale assessment [18, 19] Unintended additive noise : uncontrolled noises during speech [18] Fluency : the perceived smoothness of the sound pro- duction [18] Voicing : voicing is voiced or unvoiced where it is sup- posed to be voiced or unvoiced [18] PROs EORTC QLQ-H&N35 : European Organization for Research and Treatment of Cancer, Quality of Life Questionnaire module for patients with head and neck cancer 35-item version [11] EORTC QLQ-C30 : European Organization for Re- search and Treatment of Cancer, Quality of Life Ques- tionnaire C30 [10] All study types were included. Publications were included when at least two types of speech methods were compared. In these cases the same procedures for acoustic and perceptual evaluations are warranted for the different speaker