I was taught never to listen to the lungs and heart over clothing regardless of the gender of the patient. It can be a bit awkward with female patients, but for the more modest incline I auscultate under their top or gown.
Auscultating via clothing does muffle and add additional breath sounds cause by the movement of the diaphragm on the material, which can mast other more quieter breath sounds, murmurs etc . where I work ITU ( ICU is the US version) you do need to listen for these and be aware of them.
This is how I was taught to perform a cardiac auscultation :
Where to place your stethoscope:
Auscultation should proceed in a logical manner over 4 general areas on the anterior chest, beginning with the patient in the supine position.
The 4 percordial areas are examined with diaphragm, including:
Aortic region (between the 2nd and 3rd intercostal spaces at the right sternal border) (RUSB – right upper sternal border).
Pulmonic region (between the 2nd and 3rd intercostal spaces at the left sternal border) (LUSB – left upper sternal border).
Tricuspid region (between the 3rd, 4th, 5th, and 6th intercostal spaces at the left sternal border) (LLSB – left lower sternal border).
Mitral region (near the apex of the heard between the 5th and 6th intercostal spaces in the mid-clavicular line) (apex of the heart).
After this initial examination in the supine positions, several additional maneuvers should be accomplished in the thorough cardiac exam, as follows:
Instruct the patient to turn onto their left side (left decubitus position) and listen with the bell of the stethoscope at the apex for mitral stenosis (low pitched diastolic murmur).
Instruct the patient to sit upright and re-examine the 4 percordial regions, again with the diaphragm of the stethoscope.
Instruct the patient to lean forward, exhale, and hold their breath. Listen with the diaphragm between the second and third intercostal spaces at the right sternal (aortic) and left sternal (pulmonic) areas for aortic regurgitation.
Ideally, for Respiratory examination, the patient would be sitting.
Auscultate from side to side and top to bottom. Omit the areas covered by the scapulae.
Usually the APEX of the lungs bilaterally (2cm superior to medial 1/3 of clavicle)
Superior Lobes anterior (2nd intercostal space mid clavicular line) and posterior (Between C7 & T3)
Inferior Lobes bilaterally anterior (6th intercostal space, mid-axiallary line) and posteriorly (between T3 & T10)
Middle lobe right anterior only (4th intercostal space mid-clavicular line)
Compare one side to the other looking for asymmetry and note the location and quality of the sounds you hear.
Technique
Ask the patient to disrobe, as this will allow the stethoscope to be placed directly on the chest.
Make sure the patient is sits upright in a relaxed position, where this is possible.
You should then instruct the patient to breathe a little deeper than normal through the mouth.
The bell/diaphragm of the stethoscope is then placed against the chest wall.
Auscultation of the lungs should be systematic, including all lobes of the anterior, lateral and posterior chest.
The examiner should begin at the top, compare side with side and work towards the lung bases.
The examiner should listen to at least one ventilatory cycle at each position of the chest wall.
The examiner should identify four characteristics of breath sounds: pitch, amplitude, distinctive characteristics and duration of the inspiratory sound compared with the expiratory sound.