Magnetic Resonance Imaging (MRI) is a non-invasive medical technology that provides highly detailed images of the body’s internal structures. Tinnitus is the perception of sound, such as ringing, buzzing, or hissing, when no external sound is present. The powerful mechanical operation required to produce these images often generates acoustic noise. An MRI scan can expose a patient to noise levels high enough to cause temporary hearing changes, which may include tinnitus. This concern highlights the importance of understanding the source of the noise, its potential effects on the auditory system, and the mandated preventative measures.
Why MRI Scans Are So Loud
The intense acoustic noise produced during an MRI scan is an unavoidable byproduct of the physics necessary for image creation. The sound originates from the gradient coils, specialized components that rapidly switch their electrical currents on and off. This swift current fluctuation takes place within the scanner’s main static magnetic field, generating strong Lorentz forces. These forces cause the coil wires to vibrate mechanically, radiating outward as sound waves. The intensity of this acoustic output often reaches 120 decibels (dB) or more, which is comparable to the noise of a jet engine at takeoff or a loud rock concert. Certain advanced imaging sequences, such as echo-planar imaging (EPI), and stronger magnets, like 3-Tesla (3T) scanners, can push noise levels even higher, sometimes approaching 130 to 140 dB.
Auditory Effects of MRI Noise Exposure
Exposure to these high decibel levels poses a direct risk to the delicate structures of the inner ear. The primary effect is often a temporary threshold shift (TTS), a short-term decrease in hearing sensitivity. This temporary hearing change is frequently accompanied by temporary tinnitus, which may be perceived as ringing or a muffled sensation immediately after the scan. The noise-induced changes typically affect the cochlear outer hair cells, with hearing loss most often observed in the higher frequency ranges, specifically around 4, 6, and 8 kilohertz. While this temporary tinnitus usually resolves within minutes or hours, inadequate or improperly fitted hearing protection introduces a risk for permanent noise-induced hearing loss (NIHL) and chronic tinnitus.
Mandatory Hearing Protection During Scans
Because the noise levels inside an MRI scanner exceed established safety limits for unprotected ears, the use of hearing protection is a standard and regulated part of the procedure. The goal of this protection is to reduce the acoustic exposure at the patient’s ear to a safe level, typically below 99 dB. Standard clinical practice involves providing patients with foam earplugs, which can offer an average noise reduction of about 25 dB when properly inserted. Many facilities enhance this protection by providing dedicated MRI-safe headphones over the earplugs, especially when using higher-field-strength 3T scanners. Patients must ensure their protective gear is correctly and snugly fitted before the scan begins and remains in place throughout the procedure.
When Tinnitus Persists After an MRI
It is common for individuals to experience a mild ringing or fullness immediately following the scan due to the temporary threshold shift. This short-term tinnitus should fade quickly as the inner ear recovers from the acoustic exposure. If the perception of ringing or buzzing persists beyond 24 to 48 hours, contact a healthcare provider, such as a primary care physician or an audiologist. The doctor can perform a full hearing evaluation to assess for any persistent hearing loss, which is the underlying cause of chronic noise-induced tinnitus. Treatment often focuses on sound therapy, which uses external sounds like white noise or nature sounds to mask the internal noise, along with stress reduction and cognitive-behavioral techniques.