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Most manufacturing industries in America have hearing loss trends that move in one direction: up. Machinery Manufacturing does not. From a 2019 peak of roughly 600 annual cases, the industry has declined steadily — posting approximately 340 cases in 2024, well below pre-pandemic levels. For an industry with a 1.34% average injury rate and 719 companies in the dataset, that trend line raises a genuinely important question: what is Machinery Manufacturing doing that other industries should study?
Soundtrace analyzed nine years of OSHA ITA hearing loss data across 21,120 U.S. establishments. Machinery Manufacturing’s combination of a meaningful injury rate, a declining trend, and a workforce size that puts it outside the top-volume rankings makes it one of the more instructive sectors in the dataset. This is part of our ongoing industry-by-industry deep dive series.
Machinery Manufacturing occupies an interesting position in the occupational hearing loss landscape. Its 1.34% average injury rate places it meaningfully above the national manufacturing average, yet its relatively modest workforce of 296,670 employees means it does not produce the massive raw case volumes of Food & Beverage or Transportation Equipment. It is a high-risk sector at human scale.
The 5.5 cases-per-company figure is the most immediately useful benchmark for individual companies in this sector. It means the average Machinery Manufacturing employer recorded fewer than one hearing loss case per year over the nine-year period — a figure that appears manageable until you consider what it means at the facility level for a company with 200 or 300 enrolled workers.
A 5.5 cases-per-company average in an industry with a 1.34% rate means the rate, not the volume, is the story. A machinery manufacturer with no recordable hearing loss cases in recent years may have a strong program — or may have gaps in testing coverage that are masking threshold shifts that have already occurred.
Machinery Manufacturing is unusually heterogeneous as a noise environment. The sector spans everything from precision CNC machining shops producing surgical instrument components to heavy industrial equipment manufacturers building mining machinery and agricultural combines. The noise profile at a shop floor machining high-precision parts looks nothing like the noise profile at a facility assembling construction equipment.
What they share is that almost every production process involves metal removal, forming, or assembly operations that generate sustained noise above OSHA’s 85 dBA action level at some workstations. The specific sources, frequencies, and exposure patterns vary enormously — which is why generic hearing conservation program templates often underperform in this sector.
The high-frequency content of CNC machining noise deserves particular attention. Unlike the broadband impact noise of stamping operations, machining noise is often concentrated in higher frequency bands that are both more damaging to cochlear hair cells and more difficult to attenuate with standard foam earplugs. Workers in precision machining environments may be accumulating more hearing damage than their audiometric results initially suggest, because high-frequency threshold shifts at 3,000–4,000 Hz — the STS-relevant frequencies — often lag the initial damage at 4,000–6,000 Hz.
OSHA’s STS calculation uses 2,000, 3,000, and 4,000 Hz. Early noise-induced hearing loss typically appears first at 4,000–6,000 Hz — frequencies above the STS calculation range. A worker in a CNC machining environment can develop significant high-frequency hearing loss before it registers as a recordable STS. Annual audiograms that include 6,000 and 8,000 Hz testing provide earlier warning than OSHA-minimum test protocols.
The chart is the story. Every other manufacturing industry in the Soundtrace dataset — Food & Beverage, Transportation Equipment, Fabricated Metal, Paper & Pulp — shows either a rising trend or a COVID-disrupted pattern that recovers toward or above prior levels. Machinery Manufacturing shows something genuinely different: a pre-pandemic peak in 2019, a decline that continued through and after COVID, and a 2024 partial-year figure well below 2016 baseline levels.
The critical feature is what happened after COVID. In most industries, the 2021 and 2022 data shows a sharp recovery toward or above 2019 levels as testing programs resumed and deferred threshold shifts surfaced. In Machinery Manufacturing, the 2021 recovery is modest, and 2022 and 2023 continue declining rather than rebounding to the 2019 peak. This pattern is structurally different from a backlog-driven COVID artifact. It suggests something changed in the underlying case production rate after 2019.
The honest answer is that no single explanation fully accounts for a sustained multi-year decline in a 719-company industry. But several structural shifts are consistent with the data.
Machinery Manufacturing has been at the forefront of industrial automation — both as a producer and consumer of automated systems. CNC machining, robotic welding, and automated material handling have progressively removed operators from proximity to the highest-noise operations. A worker who previously stood at a manual grinding station for eight hours may now supervise an automated grinding cell from a control station with significantly lower noise exposure. The shift from direct machine operation to process supervision is one of the most effective engineering controls available — and Machinery Manufacturing has implemented it faster than most other sectors.
Many Machinery Manufacturing companies are mid-to-large sized independent manufacturers with EHS departments that have been building and refining hearing conservation programs for decades. Unlike food processing or forestry, where programs are often minimal or absent, a significant portion of this sector operates facilities with established noise monitoring databases, trained audiometric technicians, and long-term audiogram histories that support early threshold shift detection. Program maturity produces declining case trends as detection improves and prevention compounds over time.
Modern CNC machining centers, turning centers, and machining cells are engineered with noise enclosures, vibration damping, and reduced coolant noise as standard features — a meaningful shift from the machine tools of the 1990s and 2000s. Facilities that have invested in equipment refresh cycles over the past decade have quietly reduced their noise baseline, often without a specific noise reduction intention.
With only 296,670 total employees — a fraction of Food & Beverage’s workforce — Machinery Manufacturing’s aggregate trend can be meaningfully influenced by program improvements at a relatively small number of large companies. If the ten largest companies in the dataset materially improved their programs between 2019 and 2024, that alone could produce the observed decline without any sector-wide shift.
The declining trend is genuinely encouraging. It is also worth examining critically before interpreting it as a sector-wide success story.
First, ITA reporting population shifts. If the companies that exited or reduced their ITA reporting between 2019 and 2024 were disproportionately high-case-volume manufacturers, the aggregate would decline without any actual improvement in programs or exposures. In a 719-company dataset, this effect can be material.
Second, the high-frequency detection gap. As described above, standard OSHA-minimum audiometric testing may miss early hearing damage in machining environments. A declining STS count could partly reflect threshold shifts occurring at frequencies above the standard detection window rather than a genuine reduction in hearing loss incidence.
Third, automation-adjacent exposures. As direct machine operators move away from noise sources, maintenance technicians, tooling setters, and quality technicians — who spend time inside enclosures and adjacent to equipment during setup — may be receiving concentrated exposures that are harder to characterize with area monitoring approaches. The workers with the highest exposures may be shifting, not disappearing.
A declining trend is not a reason to reduce hearing conservation investment. It is a reason to make sure your program is designed to sustain and extend that improvement rather than reverse it. The structural shifts driving Machinery Manufacturing’s decline create new program requirements that traditional templates do not address.
Soundtrace provides in-house audiometric testing with extended frequency protocols, automated STS detection, longitudinal trend analysis, and cloud-based recordkeeping — the program infrastructure machinery manufacturers need to extend their declining trend rather than reverse it.
Get a Free QuoteWatch a DemoThe most likely contributors are increased automation reducing direct operator exposure, maturing hearing conservation programs at established manufacturers, equipment design improvements reducing ambient noise levels, and the smaller workforce size that allows improvements at a handful of large companies to move the aggregate. The decline is genuine but warrants careful interpretation.
The Soundtrace dataset shows a 1.34% average rate across 719 companies — placing it in the upper tier of manufacturing industries nationally. Despite the declining trend, this rate remains meaningfully above the national manufacturing average and warrants continued program investment.
No. Automation reduces direct operator exposure in many cases, but increases the relative exposure of maintenance technicians, tooling setters, and quality personnel who spend concentrated time inside enclosures and adjacent to equipment during setup and repair. These workers often have the highest individual exposures and are the most frequently missed by standard testing programs.
CNC machining and grinding operations produce noise concentrated in higher frequency bands. Early noise-induced hearing damage typically appears first at 4,000–6,000 Hz — above OSHA’s minimum STS calculation range of 2,000–4,000 Hz. Including 6,000 and 8,000 Hz in annual audiograms detects early damage before it progresses to a recordable STS at the standard frequencies.
Soundtrace provides in-house audiometric testing with extended frequency protocols, automated STS detection, longitudinal trend analysis across entire career audiogram histories, and cloud-based recordkeeping — giving machinery manufacturers the program infrastructure to detect early hearing changes and sustain their declining trend.