Magnetic Resonance Imaging (MRI) is a powerful medical diagnostic tool, but the process is characterized by extremely loud, repetitive noises. The source of this sound is the rapid electrical current switching within the scanner’s gradient coils. These swift changes in the magnetic field cause the coils to vibrate intensely, producing acoustic noise that can reach levels between 90 and 130 decibels, similar to a jet engine or a jackhammer. This high volume not only poses a risk to patient hearing but also contributes significantly to anxiety and discomfort, sometimes leading to failed scans. Offering the patient music is the primary method used to mitigate both the discomfort and the potential for hearing damage during the procedure.
The Necessity of Specialized Audio Systems
The powerful static magnetic field of the MRI machine dictates the strict safety requirements for any equipment brought near the patient. The field is tens of thousands of times stronger than the Earth’s magnetic field, meaning any ferrous material is strictly forbidden inside the scan room. Traditional headphones containing metal speakers and wires cannot be used because they would be violently pulled into the magnet bore, creating a dangerous projectile and disrupting the image quality.
To safely deliver audio, MRI facilities rely on specialized, non-ferromagnetic sound systems. The device that generates the sound is located outside the scan room, often in the control room with the technologist. The sound is then converted into a mechanical vibration, with the audio signal traveling through long, plastic air tubes, similar to a stethoscope, to the patient’s head.
These acoustic headphones, made entirely of plastic and foam, are designed to fit comfortably around the patient’s ears. Their primary function is hearing protection and noise reduction, offering up to 49 decibels of noise attenuation. This reduction is necessary to comply with safety regulations regarding prolonged exposure to high decibel levels. Music delivery is a secondary benefit, intended to distract the patient and further mask the residual scanner noise.
Navigating the Scan: How Music Delivery Works
The process for listening to music begins before the patient enters the scanner, as the technologist prepares the specialized equipment. The patient is typically offered a choice of music or a radio station, often selected from a playlist or streaming service controlled via a tablet or computer in the adjacent control room. The volume is set by the technologist on an external amplifier that controls the pneumatic sound delivery system.
Before the headphones are placed, the patient is often given foam earplugs, which work in tandem with the acoustic headphones to provide maximum sound dampening. The technologist then positions the non-magnetic headphones or ear-buds over the earplugs, ensuring a secure seal to maximize both noise reduction and audio clarity. The long, air-filled tubes connect these headphones to a transducer box near the magnet bore that converts the electrical music signal into sound pressure waves.
A two-way intercom system is integrated into the setup, allowing the patient to speak with the technologist at any time by pressing a call button. This communication line is crucial for patient safety and comfort. When the technologist speaks into their microphone, the music volume automatically lowers, or “ducks,” so the patient can clearly hear instructions over the sound of the scanner.
Limitations: When the Noise Overwhelms the Music
While music is an effective tool for patient comfort, its effectiveness in drowning out the scanner noise varies depending on the type of image being acquired. The MRI examination is composed of multiple distinct sequences, and the acoustic output from the gradient coils differs significantly for each one. Sequences like T1-weighted images, which are used to visualize anatomy, may produce a more moderate, rhythmic thumping sound.
However, other sequences, such as Diffusion-Weighted Imaging (DWI) or Echo-Planar Imaging (EPI), require extremely rapid and intense switching of the gradient coils. This rapid pulsing creates a much louder, high-pitched, and often continuous noise that can reach the upper end of the 110 to 120 decibel range. Even with the best noise-attenuating headphones, the music may be partially or completely overwhelmed by these intense sounds.
During these exceptionally loud sections of the scan, the music’s role shifts from providing entertainment to serving as a layer of acoustic masking. It attempts to provide a consistent, pleasant sound to focus on, rather than the sharp, startling mechanical noise. The music may also be paused entirely if the technologist needs to communicate a complex instruction, such as a breath-holding command, ensuring the quality of the image remains the priority.