MEASURE FOR REDUCTION ON SOUND AND MAGNETIC NOISE AT ULTRA-LOW FREQUENCIES BY CONNECTING PLURAL SIDE BRANCH DUCTS

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  • YAMAZAKI Keita
    Takenaka Research & Development Institute, Chief Researcher, Dr. Eng.
  • ABE Takayuki
    Takenaka Research & Development Institute, Chief Researcher

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Other Title
  • 複数のサイドブランチを用いた広帯域の超低周波音，磁気雑音の対策とその評価
  • 複数のサイドブランチを用いた広帯域の超低周波音,磁気雑音の対策とその評価 : 磁気シールドルームの磁気ノイズとなるグラスウールダクトの超低周波共鳴およびその対策に関する研究(その2)
  • フクスウ ノ サイドブランチ オ モチイタ コウタイイキ ノ チョウテイシュウハオン,ジキ ザツオン ノ タイサク ト ソノ ヒョウカ : ジキ シールドルーム ノ ジキ ノイズ ト ナル グラスウールダクト ノ チョウテイシュウハ キョウメイ オヨビ ソノ タイサク ニ カンスル ケンキュウ(ソノ 2)
  • No. 2 Study and measure on air fluctuation due to mechanical resonance of glass wool duct resulting in weak magnetic noise at ultra low frequencies in a magnetically shielded room
  • 磁気シールドルームの磁気ノイズとなるグラスウールダクトの超低周波共鳴およびその対策に関する研究　(その２)

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Abstract

Although microtremors transmitted from the concrete floor can be reduced by the Active Microtremor Isolation system (ACMI) installed underneath the magnetically shielded room (MSR), weak but significant magnetic noises at frequencies of less than 20 Hz were still detected by SQUID magnetometers when the MSR was being air-conditioned. This magnetic noise was identified to be due to microtremors caused by sound pressure from the mechanical resonances of glass wool duct at low frequencies. In this paper, five of side branch ducts were connected to the main duct to reduce such sound pressure, microtremor and magnetic noise in the MSR. We compared the measured frequency dependencies of sound pressure, inner-wall vibrations, and magnetic noise in the MSR, with and without the side branch duct.

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