Air escaping underneath cough-relief valve
This might happen when the patient is giving too high pressure for speaking. In that case one hears air blowing underneath the cough-relief valve, the valve opens sometimes during speaking, or valve makes a whistling noise. First check whether the valve is in its strongest position. When the problem still exists in the strongest position try to teach the patient to speak softer and with lower pressure. Usually the patient manages to keep the cough-relief valve closed during speech within a couple of days; the cough-relief valve serves as a 'feedback' mechanism to lower pressure. In case of severe hypertonicity or spasm it should be considered to treat the hypertonicity.