When auscultating the lungs, it is important to use a systematic side-to-side approach, place the stethoscope directly on bare skin, and listen in a quiet room with the patient sitting upright. These fundamentals sound simple, but skipping any one of them can cause you to miss faint but clinically significant sounds like fine crackles or subtle wheezing.
Room and Patient Setup
Auscultation should be performed in a quiet room. Background noise from televisions, monitors, or conversation can easily mask the soft sounds you’re trying to detect. Have the patient sit upright in a relaxed position whenever possible, as this allows full expansion of both lungs and gives you access to the anterior, lateral, and posterior chest. If the patient cannot sit up, roll them from one side to the other to examine the back.
Ask the patient to disrobe or open their gown so the stethoscope can be placed directly against the skin. Auscultating through clothing, even a single layer, muffles findings and can cause you to miss faint crackles or subtle changes in breath sounds. A Baylor University Medical Center review noted that any clothing between the stethoscope and skin “might lead to serious failures in diagnosing heart or lung pathology.” If full removal isn’t practical, at minimum slide the stethoscope underneath the fabric to make direct skin contact.
Breathing Instructions
Instruct the patient to breathe slowly and deeply through an open mouth. Nose breathing creates turbulent airflow in the nasal passages that generates its own sound, which can be transmitted down the airway and interfere with what you hear at the chest wall. Mouth breathing moves air more directly and produces cleaner breath sounds for evaluation. Remind the patient to breathe a little deeper than normal but not to hyperventilate, as prolonged deep breathing can cause lightheadedness.
Which Part of the Stethoscope to Use
Use the diaphragm (the flat side) of the stethoscope for lung auscultation. Lung sounds are generally higher in frequency, and the diaphragm is designed to pick up high-frequency sounds more effectively. The bell side amplifies low-frequency sounds and is better suited for certain heart sounds. Press the diaphragm firmly and flat against the skin to create a good seal, which improves sound transmission and reduces artifact from the stethoscope shifting.
The Side-to-Side Listening Pattern
The single most important technique in lung auscultation is comparing one side to the other. Start at the top of the chest and work downward, but alternate between the left and right sides at each level before moving down. This side-to-side comparison lets you detect asymmetry, which is often the first clue that something is wrong. A wheeze heard only on the right, or breath sounds that are diminished on one side, stands out immediately when you’ve just listened to the same spot on the opposite lung.
On the anterior chest, begin above the clavicles at the lung apices, then move to the second intercostal space (roughly below the middle of the collarbone), then continue downward. On the right side, include the middle lobe area around the fourth intercostal space. Continue to the sixth intercostal space along the side of the chest for the lower lobes.
On the posterior chest, start between the top of the shoulders and work down to about the level of the tenth thoracic vertebra, which corresponds roughly to the bottom of the shoulder blades and below. Skip the areas directly over the scapulae, as the thick bone and muscle there block sound transmission. The posterior chest gives you the best access to the lower lobes, which make up the largest portion of lung tissue and are where fluid and secretions tend to collect.
Normal Breath Sounds to Recognize
Knowing what normal sounds like is essential before you can identify what’s abnormal. There are three types of normal breath sounds, and each belongs in a specific location.
- Vesicular sounds are soft, low-pitched, and rustling. They’re heard over most of the peripheral lung fields. The inspiratory phase is longer than the expiratory phase, and the sound fades out gently. This is what you should hear over the majority of the chest.
- Bronchial sounds are louder, higher-pitched, and hollow. They’re normally heard only over the trachea and the large central airways. The expiratory phase is longer and louder than inspiration. If you hear bronchial sounds out in the peripheral lung fields, that suggests the lung tissue between the airway and your stethoscope has become solid (consolidated), as happens with pneumonia.
- Bronchovesicular sounds fall between the two. They have equal inspiratory and expiratory phases and are normally heard near the sternum in the first and second intercostal spaces, and between the shoulder blades posteriorly, where the large bronchi are closest to the chest wall.
Abnormal Sounds and What They Suggest
Abnormal (adventitious) breath sounds layer on top of normal breathing and fall into a few categories. Noting when they occur in the breathing cycle, whether on one side or both, and whether they’re high or low pitched all help narrow down the cause.
Crackles are brief, popping or clicking sounds. Fine crackles sound like hair being rubbed between your fingers near your ear and typically occur during inspiration. They suggest fluid in the small airways or early scarring of lung tissue, as in pulmonary fibrosis. Coarse crackles are louder, lower-pitched, and more gurgling. They point to secretions in the larger airways, as in bronchitis or pneumonia. The number of crackles and their timing during inspiration can help distinguish between conditions.
Wheezes are continuous, musical sounds produced by air passing through narrowed airways. High-pitched wheezes (above roughly 200 Hz) are the classic sound of asthma or reactive airway narrowing. They’re most common during expiration but can occur during both phases when narrowing is severe. Low-pitched wheezes are sometimes called rhonchi and have a snoring quality. They often indicate mucus or secretions in the larger airways and may clear or change after coughing.
Diminished or absent breath sounds on one side are just as important as any added sound. They can indicate a collapsed lung, a large pleural effusion (fluid around the lung), or severe air trapping as in emphysema.
Vocal Resonance Tests
When you hear something abnormal, vocal resonance tests can help confirm whether lung tissue has consolidated or fluid has collected around it. These are performed while continuing to listen with the stethoscope on the chest.
- Egophony: Ask the patient to say “Eee.” Over normal lung, you hear “Eee.” Over consolidated or fluid-filled areas, the sound changes to an “Ay” with a nasal, bleating quality. This shift is a reliable sign of pneumonia or pleural effusion.
- Bronchophony: Ask the patient to say “ninety-nine.” Over healthy lung, the words sound muffled and indistinct. Over consolidated tissue, the words become louder and clearer.
- Whispered pectoriloquy: Ask the patient to whisper “one-two-three.” Whispered words are normally almost inaudible through the stethoscope. If you can hear them clearly, it strongly suggests consolidation beneath that spot.
All three tests work on the same principle: solid or fluid-filled tissue transmits sound more efficiently than air-filled lung. A positive result on any of them in a specific area should prompt further evaluation of that region.
Common Mistakes That Affect Accuracy
Listening through clothing is the most frequent error and the easiest to avoid. Even a thin hospital gown can obscure fine crackles. Other common pitfalls include listening in a noisy environment, failing to compare side to side (which makes asymmetry invisible), and rushing through the exam without covering all lung fields. Skipping the posterior bases is particularly problematic because gravity pulls fluid and secretions downward, making the lower posterior fields the most likely place to hear early crackles from fluid overload or developing pneumonia.
Pressing too hard with the stethoscope can also be an issue, especially over bony areas like the ribs and spine, where it creates friction artifact that mimics crackles. Use firm but comfortable pressure, and if you hear something unusual, ask the patient to cough and listen again. Sounds caused by secretions in the airways often change or disappear after a cough, while crackles from fluid in the lung tissue or fibrosis persist.