susurration

[Middle English susurracioun, from Late Latin susurrātiō, susurrātiōn-, from Latin susurrātus, past participle of susurrāre, to whisper, from susurrus, whisper, ultimately of imitative origin.]

noun

A low, indistinct, and often continuous sound: mumble, murmur, sigh, sough, susurrus, whisper. See sounds/pleasant sounds/unpleasant sounds/neutral sounds or silence.

An auscultatory sound, particularly a periodic sound of short duration of cardiac or vascular origin.

• anemic m. — see blood murmur (below).
• aortic m. — a sound indicative of disease of the aortic valve.
• apex m. — one heard over the apex of the heart.
• arterial m. — one in an artery, sometimes aneurysmal and sometimes constricted.
• blood m. — one due to an abnormal, commonly anemic, condition of the blood. Called also anemic murmur.
• cardiac m. — see heart murmur (below).
• cardiopulmonary m. — one produced by the impact of the heart against the lung.
• continuous m. — a humming murmur heard throughout systole and diastole.
• crescendo m. — one marked by progressively increasing loudness.
• crescendo–decrescendo m. — one with increasing intensity until mid- to late systole, then a decreasing intensity, giving a diamond-shaped tracing on phonocardiography. Characteristic of pulmonary stenosis.
• decrescendo m. — one with an intensity that gradually decreases. Heard during diastole in aortic or pulmonary valvular insufficiency.
• diamond-shaped m. — refers to the phonocardiographic tracing of a crescendo–decrescendo murmur.
• diastolic m. — one at diastole, due to mitral obstruction or to aortic or pulmonary regurgitation.
• ejection m. — systolic murmur heard predominantly in mid-systole, when ejection volume and velocity of blood flow are at their maximum.
• friction m. — friction rub.
• functional m. — a cardiac murmur occurring in the absence of structural changes in the heart.
• heart m. — any adventitious sound heard over the region of the heart. It may indicate a leaking or stenotic valve, a congenital patency between the right and left sides of the heart, or be a functional murmur which does not indicate cardiac disease. These occur in young foals, some of them disappear before maturity.
• hemic m. — see blood murmur (above).
• innocent m. — one caused by increased velocity of blood rather than a cardiac lesion.
• machinery m., machinery-like m. — a long, rumbling sound occupying most of systole and diastole. Characteristic of patent ductus arteriosus and arteriovenous fistulas.
• mitral m. — one due to disease of the mitral valve.
• musical m. — a cardiac murmur having a periodic harmonic pattern.
• organic m. — one due to structural change in the heart.
• pansystolic m. — one heard throughout systole.
• prediastolic m. — one occurring just before and with diastole, due to mitral obstruction or to aortic or pulmonary regurgitation.
• presystolic m. — one occurring shortly before the onset of ventricular ejection, usually associated with a narrowed atrioventricular valve.
• pulmonary m. — one due to disease of the valves of the pulmonary artery.
• radiating heart m. — one which is heard over a wider area or over another area. The systolic murmur of subaortic stenosis radiates up the aortic arch and carotid arteries. It can be heard over the right, as well as left, heart base and occasionally over the head.
• regurgitant m. — one due to a dilated valvular orifice, with consequent regurgitation of blood through the valve.
• seagull m. — a raucous murmur resembling the call of a seagull, frequently heard in aortic insufficiency.
• systolic m. — one occurring at systole, usually due to mitral or tricuspid regurgitation, or to aortic or pulmonary obstruction.
• tricuspid m. — one caused by disease of the tricuspid valve.
• vascular m. — one heard over a blood vessel.
• vesicular m. — the normal breath sounds heard over the lungs.

The noun has 2 meanings:

Meaning #1: the indistinct sound of people whispering
  Synonym: susurrus

Meaning #2: speaking softly without vibration of the vocal cords
  Synonyms: whisper, whispering