<prompt> all are true about s1 exceptlower frequency than s2caused by closure of mitral valveheard at the end of ventricular systolebetter heard with diaphragm of stethescope  <response>: CHARACTERISTICS OF S1 Normally heard as fused single hea sound Medium to High Frequency Low Pitched Best heard with diaphragm M1 louder than T1 M1 best heard at apex T1 best heard at Left LSB Splitting can be heard in Expiration and L-LSB ref : harrisons 21st ed 