The high-pitched roar noted in these 767-300ER and 767-400ER recordings is a function of engine architecture rather than an anomaly, and the observation tracks closely with what's well understood about the aircraft's powerplant options. The 767 family was certified with a choice of three engine types depending on customer selection: the Pratt & Whitney PW4000, the General Electric CF6-80, and the Rolls-Royce RB211. Each produces a distinct acoustic signature, and the PW4000-equipped variants are frequently described by enthusiasts and line pilots alike as having a sharper, more piercing tone compared to the deeper, more resonant note of the CF6-powered jets. This is largely attributable to bypass ratio, fan blade count and geometry, and the specific compressor/turbine staging Pratt & Whitney used in the 4000 series, all of which shape the frequency content of both the fan noise and the core exhaust noise heard on approach and during high-thrust ground operations.
The pitch is especially pronounced on landing for a specific aerodynamic and operational reason: during approach and flare, engines are typically at or near idle, and the dominant noise source shifts from jet exhaust velocity (which dominates at takeoff power and tends to mask higher frequencies) to fan and compressor whine, which is more tonal and higher in pitch. On the PW4000, this idle-thrust whine is often more noticeable because of the engine's specific fan design and the acoustic treatment (or relative lack thereof compared to more modern high-bypass designs) in the nacelle. Reverse thrust deployment after touchdown adds another layer, as the redirected airflow and associated turbulence generate additional high-frequency content that can make the 767 sound notably shriller than aircraft with more heavily bypassed, quieter-running engines like later CFM or GE9X-class powerplants.
For working pilots, this kind of acoustic signature has practical relevance beyond trivia. Engine sound characteristics are one of the informal cues line pilots and mechanics use for situational awareness — a change in pitch, a new whine, or an asymmetric tone between engines can be an early indicator of a developing mechanical issue, icing on inlet components, or an FOD event, even before instrumentation flags it. Crews who fly PW4000-powered 767s or similarly configured legacy widebodies (including certain 747-400s and A300/A310s sharing PW4000 lineage) develop familiarity with what "normal" sounds like for that specific engine family, which aids in anomaly recognition. This also ties into noise abatement procedures and community noise complaints, which remain an operational consideration for cargo carriers like UPS and FedEx, both of which operate large PW4000-powered 767-300ER freighter fleets on nighttime and early-morning schedules into noise-sensitive airports.
More broadly, this observation reflects a larger trend in commercial aviation: the gradual retirement of first- and second-generation high-bypass turbofans in favor of ultra-high-bypass designs (like the CFM LEAP, PW1000G GTF, and GE9X) specifically engineered to reduce both overall noise levels and the harsh tonal characteristics that make legacy engines like the PW4000 stand out to observers. As 767-300ERs age out of passenger service and increasingly transition to freighter roles — a trend accelerated by Amazon Air, UPS, and FedEx demand — their distinctive high-pitched roar will likely become an increasingly nostalgic marker of legacy widebody operations, much as the JT8D's sound is now associated with a bygone era of narrowbody flying. For pilots and enthusiasts alike, these sonic signatures serve as an audible timeline of turbofan engineering evolution, from the loud, tonal designs of the 1980s to the quieter, geared and ultra-high-bypass engines now populating current-production aircraft.