Why The Embraer E175's Thrust Sounds Loud For A Regional Jet

Based in the UK, Josh is a keen writer with a degree in Military History. Having worked previously as a financial journalist, he has covered the aviation industry extensively, reporting on airlines' results and monthly passenger statistics in the aftermath of the pandemic, alongside the likes of regulation around sustainable fuels, and the prospects for hydrogen-powered commercial flight. He joins Simple Flying with a lifelong love of all things aviation.

The Embraer E175 has come to be a vital cog in the machine that is the worldwide aviation network. Well positioned to serve regional travel markets and feed passengers into larger hub-and-spoke systems, the E175 has found success in all corners of the world over its 20 years of production.

But time has caught up to the E175 in one sense. Today, noise is a big consideration for regulators, airlines, airports, and manufacturers alike. While the E175 complies with current regulations on sound levels, newer models in its class are increasingly outperforming it on noise.

The Embraer E175

The E175 itself was among Embraer's answer to serving the short- to medium-haul space and bridging the gap between smaller regional jets and mainline narrowbodies. Developed as a stretched version of the E170, the E175 is among four aircraft that make up the E-Jet family today. The E175 program launched in 1999, and the first model flew commercially with Air Canada in 2005.

Overall, the E-Jet family has enjoyed resounding success over its two-plus decades of service. According to Key.Aero, over 1,700 examples had rolled off the production line as of December last year, incorporating 196 E170s and 805 E175s, as well as 570 and 173 larger E190s and E195s, respectively.

The E175 has proven to be the most popular in the E-Jet series. Come December, 781 of the jets remained in active service, against 144 E170s, 399 E190s, and 129 E195s. The E175 remains in production, unlike its counterparts from the original E-Jet line, thanks to strong demand, particularly in the US, where it holds an approximate 80% share of the regional jet segment, according to the Ready For Take-Off Book. But despite the accolades that have kept the model in production over the years, the E175 is by no means a quiet plane by modern standards.

Embraer E175 Loud By Modern Standards

It is important to note that, by modern standards, the E175 can be considered loud. Against its closest competitor historically, the Bombardier CRJ900, the E175 is relatively close in terms of noise. According to European Union Aviation Safety Agency type certification documents, an E175 weighing 85,517 pounds (38,790 kg) at takeoff was measured as producing 84.4 decibels of effective perceived noise during a flyover in 2025, for example. A CRJ900 of similar weight was recorded as producing 83.9 decibels, based on documents from two years earlier.

But an aircraft's loudness can vary by perspective and flight phase. The former matters because cabin noise affects passenger comfort and can even impact the health of those onboard. For instance, research from finance and travel site US Credit Card Guide shows the giant, four-engined Airbus A380 as being significantly quieter from a passenger’s point of view than the E175. From outside either aircraft, the A380 would naturally be louder, as the heavier model requires more thrust to get airborne.

Interestingly, widebody aircraft tend to be quieter from within the cabin than narrowbodies, despite being heavier and requiring more thrust from more powerful engines. This is often simply because passengers sit farther from the engines, and models like the A380 also incorporate technologies to absorb noise in cabins and engines. The E175’s cabin is louder than several widebodies, which helps explain why. What it does not explain, though, is why models from within the same regional class but produced more recently are also quieter.

Embraer E175 Versus Newer Regional Rivals

It is when such newer, comparable models are factored in that the disparity becomes clear. Namely, the Airbus A220 is another that bridges the gap between regional and mainline narrowbody models, albeit towards the larger end of the spectrum than the E175. Nonetheless, the A220 offers a useful basis of comparison thanks to its relatively recent, clean-sheet design.

Developed as the Bombardier CSeries before Airbus bought a majority stake in the program in 2018, the A220 entered commercial service in 2016, two years earlier. That means the A220 incorporates more modern technology in comparison to the E175, including newer-generation geared turbofan Pratt & Whitney PW1500G engines. Among other things, the PW1500G has a gearbox between its fan and low-pressure core, allowing each to spin at an optimal speed — with the fan turning slower and helping reduce the aircraft’s noise footprint.

Overall, the A220 is considered one of the quietest commercial aircraft in service today. According to Airbus , the aircraft type's noise footprint is as much as 50% smaller than previous-generation aircraft. Against International Civil Aviation Organization (ICAO) standards introduced in 2006, which the E175 is said to “meet or surpass,” the A220’s difference is 18 effective perceived noise decibels. That is enough of a difference to hear, particularly against aging counterparts, according to aviation consultancy AirInsight. But it is not just the gear system that aids the PW1500G in being quieter. Bypass ratio is a major factor.

Bypass Ratio A Big Factor In Engine Noise

Embraer’s E175 is powered by two CF34-8E engines from GE Aerospace. Like the E175 itself, development of the CF34-8E began in the late nineties. As such, the engine is in many ways a product of its time. That includes its bypass ratio.

Equated to the ratio between the mass flow rate of air bypassing and the mass flow rate entering the engine core, bypass ratio plays a major role in both efficiency and noise. Air that enters the core is compressed before being mixed with fuel and combusted. The resulting hot gases then drive turbines, which are connected to the fan via a shaft. The fan, in turn, produces most of the thrust. That means a higher-bypass engine accelerates more air around its core than through it. Consequently, less reliance is placed on high-velocity exhaust gases from the core — a significant source of jet engine noise — to produce thrust.

*Automatic power reserve for added thrust in case of engine failure

By today’s standards, the CF34-8E’s 5:1 bypass ratio is low. The A220’s PW1500G, with a 73-inch (185.4 cm) fan diameter, far exceeds that, with a bypass ratio of 12:1. In practice, the CF34-8E relies on proportionally more air passing through its core to produce up to 14,500 pounds-force (64.5 kN) during takeoff. The A220 isn't the only aircraft to adopt higher-bypass engines; the technology is becoming increasingly common across the commercial industry, including on Embraer’s newer models.

Embraer’s Newer E2 Also Quieter

The Embraer E-Jet E2 series has emerged as the direct successor to the manufacturer’s widely successful E-Jet family. Launched in 2013, the E190-E2 and the first of the new variants entered commercial service in 2018, before the E195-E2 in 2019. More modern engine technology has helped create more efficient and quieter variants than those in the original E-Jet series.

In fact, the E2 is said to be one of the quietest families of commercial aircraft around today, alongside the A220, according to AirInsight. Interestingly, each E2 uses engines from within the same Pratt & Whitney family as the A220. For the E190-E2 and E195-E2, this is the PW1900G geared turbofan, which measures 73 inches (185.4 cm) in fan diameter and has a 12:1 bypass ratio.

Once in service, the Embraer E175-E2 will also use Pratt & Whitney engines — in this case the purpose-built PW1700G. These are set to boast a fan of 56 inches (142.2 cm) in diameter and a bypass ratio of 9:1, to produce between 14,000 and 17,000 pounds-force (62.28 and 75.62 kN) of thrust. The result should be a successor that trumps the original E175 on noise.

But Noise Levels Do Vary On Any Aircraft

The elephant in the room is that noise levels vary on any aircraft for several reasons. Where you sit plays a large part; for instance, seats toward the back of an aircraft are naturally subject to more sound, whether it's sent backward from wing-mounted engines or comes from rear-mounted engines, like on the CRJ900.

Flight phase also has a huge effect. Takeoff is often one of the loudest parts of a flight, since engines have to run at high thrust settings. As such, this is when differences in noise levels between aircraft are easier to pick up, and when the E175 may appear surprisingly loud for a regional jet in particular.

Both Embraer and GE Aerospace were approached for comment by Simple Flying.