This is one of the true arts of veterinary medicine and one you should aspire to excel at as an emergency clinician! You should divide the chest up into cranial, middle and caudal, and dorsal, middle and ventral and auscult each area. Lung sounds should be louder in the cranioventral portion of the chest and symmetrical from left to right. Ignore the heart when you are listening to the lungs and vice versa. If the animal is taking deeper breaths than normal then lung sounds should be louder than normal. So your job is to work out are the lung sounds the correct volume for the tidal volume and effort. An animal that is tachypnoeic from pain, stress or exercise should have louder lung sounds than at rest.