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Description
Accurate prediction of heat pump noise requires acoustic source data that go beyond A-weighted overall sound power levels. For outdoor units of air source heat pumps, frequency-dependent directivity is particularly relevant, since fan openings, heat exchangers, blind faces and top surfaces can radiate differently and therefore influence receiver levels depending on installation orientation.This contribution presents recent progress in IEA HPT Annex 63, “Placement Impact on Heat Pump Acoustics”, and builds on earlier work presented at Forum Acusticum. The open Annex 63 database has been expanded with additional measurements from several laboratories and combines frequency- and face-resolved sound power data with metadata on unit geometry, operating conditions and measurement methodology. Each entry contains one-third-octave-band partial sound power levels for five standardized unit faces, enabling comparisons between units and laboratories. Data from ISO 9614 sound intensity measurements, ISO 3744 sound pressure measurements using cubic enveloping surfaces, and ring- or dome-array measurements in free field over a reflecting plane are harmonized through defined conversion procedures.Particular emphasis is placed on acoustic directivity and its relevance for placement. A cross-laboratory analysis of five comparable units at A7W55, with fan and heat exchanger on opposite faces and three blind faces, shows systematic face-dependent radiation patterns. Blind faces provide broadband shielding of approximately 5 dB below 2 kHz, while heat-exchanger faces radiate about 10 dB more than fan faces above 2 kHz.With Annex 63 concluding in September, the presentation summarizes the database status, harmonization methods, conversion challenges, key acoustic findings and the outlook toward generic source models for improved heat pump noise prediction.