A question often asked by ultrasound inspectors concerns the impact the steady use of ultrasound detectors might have on their hearing. Inspectors should be concerned. Safety is their first right, but everyone needs to own this. Inspectors spend hours in areas that produce constant, deafening background noise. Manufacturers of ultrasound instruments and employers of these inspectors owe it to protect their safety.

Governments also play a role. The United States Department of Labor (OSHA), the Canadian Centre for Occupational Health and Safety (CCOHS), and le Santé et Sécurité au Travail (translates to: Worker’s Health and Safety and carries the abbreviation INRS) all publish acceptable, non-negotiable exposure limits for noise. Here are the tables from European Union, Canada, and the USA.

List of legislated noise exposure in the United States
List of legislated noise exposure in European Community
List of acceptable noise exposure by province

Compliance Responsibility

Here are some ways employers ensure compliance to government regulated safety standards for noise exposure while protecting their employees.

  1. Post signage in high noise zones where hearing protection is mandatory and enforce it with penalties.
  2. Provide employees and visitors with access to approved hearing protection at the entrance to high risk zones.
  3. Conduct regular noise level inspections to ensure compliance and document the results.
  4. Educate employees about their rights and how to protect this important sense.

Safety doesn’t begin, nor end with the employer and the government. It extends to the manufacturer of instruments who also must take responsibility for the goods they produce. Does your ultrasound gun meet the standard of safety your employees deserve? Let’s take a quick look at how an ultrasound detector works to gain a better understanding of the potential risk.

Ultrasound Instruments

The Detector/Processor

An ultrasound detector, whether a gun, or a meter, is an electronic system designed to detect high frequency sounds and convert them to audible sounds. Many plant defects produce sound signals with peaks around 40kHz. The ability to detect, measure, and listen to these defects empowers us to find problems that impact uptime and energy costs. An ultrasound detector is considered the first line of defense in the battle for more reliable and profitable plants.

Inaudible sound pressure waves — around 40kHz — are inconsequential to human hearing. They are produced by Friction, Impacting, and Turbulence. They share three common characteristics in that they are high frequency, short wavelength, and low amplitude. As such, they don’t travel far from their source and are attenuated quickly by their transport medium. On their own, they pose no threat to human hearing.


Ultrasound detectors hear ultrasound with medium-high frequency piezo crystal sensors. Stimulated by the wave’s energy, the crystal produces an extremely low-energy electric voltage. This weak signal is first amplified, and then heterodyned by the ultrasonic meter. Don’t panic, heterodyned is just a fancy word that describes the process of converting inaudible ultrasound into audible sound. Once converted, the signal is made available to the inspector as a measured value, a time waveform and spectral display, and of course audibly, through the headphone output. 


Inspectors listen with headphones provided with the instrument. The quality and style of these headphones vary from one manufacturer to another. The key features to look for are:

  • Do they provide sufficient hearing protection from external noise?
  • Do they provide a rich, high-quality sound experience?
  • Do they come equipped with volume adjustment, independent of instrument amplification?

Walkman Style

Walkman style headphones should not be used in industrial workplaces. These foam-covered earpieces have poor sound quality and provide no external hearing protection to the inspector. They are typically supplied with low-cost, low quality instruments. If an ultrasound instrument comes equipped with this style of headset, it is unlikely the manufacturer went to the additional care and expense to implement independent volume controls. 


Over-the-ear headphones are available in varying quality as well; once again depending on the manufacturer. Higher quality headphones, such as those made by 3M and supplied exclusively by SDT Ultrasound Solutions, provide rich sound quality while providing external hearing protection that exceeds requirements imposed by the USA, EU, and Canadian governments. It’s definitely worthwhile to do your homework and make sure the headset supplied with your ultrasound system are rated to block audible plant noise from reaching your ears.

How Does SDT Work to Protect Your Hearing?

SDT Ultrasound Solutions has a 45+ year history of providing high quality instruments. This Belgian based manufacturer has, at times, been accused of over-engineering their products, but makes no apologies when it comes to the safety of their customers. 

Each ultrasound instrument must meet stringent quality and safety standards before it can be released to sell. These standards are engineered at the design concept and rigidly tested and confirmed at the assembly and final production stages. The following declaration applies to SDT200, SDT270, SDT340, LUBExpert, and Checker Range of products. 

SDT Commercial Declaration

During design, assembly, and production, SDT takes into consideration noise exposure and the health and safety protection of its customers. 

We therefore declare, under our own responsibility, that:

SDT200, SDT270, SDT340, LUBExpert, and Checker Range ultrasound instruments deliver a maximum sound pressure level (SPL) of 79dB typical, when used with the headsets supplied by SDT. This declaration is made regardless of the measurement level and/or the audio volume level as adjusted by the user. 

SDT makes an additional safety guarantee to our users. When connecting any SDT sensor, or selecting/changing sensors, our instruments automatically self-adjust to a default, maximum sound pressure level of 58dB typical. This applies to all compatible, SDT manufactured sensors. This auto adjustment is done voluntarily by SDT, for the protection and safety of anyone who uses our products. 

An audio volume adjustment, which is independent to the signal amplification setting, is a standard feature of all current SDT instruments. This feature enables each operator to adjust the headset volume in a safe, comfortable, and personalized way, without compromising the measurement accuracy of the instrument. 

Through the design and engineering of our instruments, it is our intention to meet or exceed safety standards at every level. We are proud to know that all instruments mentioned in this declaration fall within the guidelines set forth by Canadian, American, and European government safety bodies. 

Final Thoughts


Ultrasound inspectors are exposed to some of the highest noise levels found in their facility. Safety and prevention of hearing loss should be a considering factor when selecting an ultrasound instrument, or using one already on hand. Government legislated exposure levels must be respected by employers, employees, and instrument manufacturers. 

It is not enough for manufacturers to simply make a self-declared statement of compliance. They must be prepared to back up their declaration with documented testing procedures and results. Don’t compromise your hearing. Before you venture into the plant with your ultrasound gun, ask the manufacturer if the headphone output respects the noise level exposure prescribed by OSHA, CCOHS, and INRS.

Stay safe and Hear More! 

2 thoughts on “Is Your Ultrasound Gun Making You Deaf?”

  1. But it sounds impossible: how can sounds you cannot hear damage your hearing? Lots of research has been done on this topic, but very little has been found to indicate that either infrasound or ultrasound can cause hearing loss. Infrasound Infrasound is ubiquitous and intense: in a car you can easily be exposed to low frequency sound in excess of 100 dB, even though it barely registers on the A scale, which is weighted for human hearing.

    1. Thanks for your question. In this case it is just a slight confusion. We are talking about the audible, heterodyned signal (post-processed) that the user can listen to in the headphones. SDT takes extra precaution to protect the users’ hearing by limiting the amplification of the output to below 80dBA. For more information about SDT visit https://sdtultrasound.com/products/sdt340/

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