Fig. 4From: Endoscopic treatment of anterior laryngeal web using keel designed from ePTFE followed by voice therapy: a refined techniqueThis figure shows the outcomes of acoustic voice parameters after operation. Note the significant improvement of all voice parameters (increase of HNR and decrease of other parameters). HNR: harmonics-to-noise ratio, PPQ: pitch perturbation quotient, APQ: amplitude perturbation quotient. Preop: preoperative, Postop: postoperative, **P < 0.01Back to article page