Acoustic Flow Duct

For the generation of high-intensity pure tones (up to 155 dB at frequencies ranging from 500 to 6000 Hz) and for broadband noise (SPLs up to 125 dB per 1/3-octave band in the reverberant rooms), high performance Altec loudspeakers in combination with a supersonic jet are used. Yet another way to use a horn.

Found at the NLR pages.