Category B - full version without watermark 720x576 (check terms and conditions at www.teledesign.de) The embed version with watermark is free of charge. - Description: In the upper neck area, the two vocal cords span the cavity of the larynx. They consist of complex muscle and tissue layers which can be adjusted in position. During voice change -- around the age of 11 to 15 years -- the vocal cords get thicker and longer in girls and boys. The median pitch of the voice lowers by one octave in boys, in girls by one third. The vocal range increases to about two octaves. The vocal cords close the trachea almost completely. The air stream during exhalation makes them vibrate and with the help of muscles, cartilage and joints the tone is created.