with inhalation. the decreased (more negative) intrathoracic pressure has an opposite effect on the left side of the heart, making it harder for the blood to exit into circulation. therefore, left-sided murmurs generally decrease in intensity during inhalation. increasing venous blood return to the right side of the heart by raising a patient's legs to a 45-degree while lying supine produces similar effect which occurs during inhalation. inhalation can also produce a non-pathological split s2 which will be heard upon auscultation. with exhalation, the opposite haemodynamic changes occur: left-sided murmurs generally increase in intensity with exhalation. interventions that change murmurs main article: heart murmur there are a number of interventions that can be performed that alter the intensity and characteristics of abnormal heart sounds. these interventions can differentiate the different heart sounds to more effectively obtain a diagnosis of the cardiac anomaly that causes the heart sound. other abnormal sounds clicks – heart clicks are short, high-pitched sounds that can be appreciated with modern non-invasive imaging techniques. rubs – the pericardial friction rub can be heard in pericarditis, an inflammation of the pericardium, the sac surrounding the heart. this is a characteristic scratching, creaking, high-pitched sound emanating from the rubbing of both layers of inflamed pericardium. it is the loudest in systole, but can often be heard at the beginning and at the end of diastole. it is very dependent on body position and breathing, and changes from hour to hour. surface anatomy the aortic area, pulmonic area, tricuspid area and mitral area are areas on the surface of the chest where the heart is auscultated. heart sounds result from reverberation within the blood associated with the sudden block of flow reversal by the valves closing. because of this, auscultation to determine function of a valve is usually not performed at the position of the valve, but at the position to where the sound waves reverberate. aortic valve (to aorta)right second intercostal spaceupper right sternal border pulmonary valve (to pulmonary trunk)left second intercostal spaceupper left sternal border erb's pointleft third intercostal spaceleft sternal border tricuspid valve (to right ventricle)left fourth, fifth intercostal spaceslower left sternal border mitral valve (to left ventricle)left fifth intercostal spaceleft midclavicular line recording heart sounds using electronic stethoscopes, it is possible to record heart sounds via direct output to an external recording device, such as a laptop or mp3 recorder. the same connection can be used to listen to the previously recorded auscultation through the stethoscope headphones, allowing for a more detailed study of murmurs and other heart sounds, for general research as well as evaluation of a particular patient's condition.