The mixtures of potassium salt of aromatic compounds such as benzoic acid, terephthalic acid and
salicylic acid and potassium perchlorate were widely used as a pyrotechnic whistle composition.
In this report, the reactions of pyrotechnic whistle compositions of the mixtures of potassium
benzoate with potassium perchlorate were investigated by thermal analysis, observation by microscope
and sound test such as the waveform, frequency and sound pressure analysis of the whistling
noise for different compositions, tube length and material of tube. The results obtained are as follows :
(1)The compositions capable for producing whistling noise are the mixtures of potassium benzoate
with potassium perchlorate which compositions are in the proportions 40 / 60, 30 / 70, and 20 / 80
(C6H5COOK / KClO4 by wt.).
(2)The fundamental frequency of the pyrotechnic whistling noise is about 2 kHz, and harmonic sound
appears beside the fundamental sound. The frequency is inversely proportional to the length of
tube. Therefore, whistling noise was considered to appear by the resonance of the tube.
(3)Although different materials were used for the tubes, they made little difference in frequency and
linear burning rate, when whistling compositions pressed into the aluminum, glass, and vinyl chloride tube.
The sound pressure increases about 10 dB louder cmpared to that one which pressed into the paper tube.
現在, 煙火の笛薬は, 安息香酸, テレフタル酸, サリチル酸などの芳香族化合物のカリウム塩と過塩素酸カリウムとの混合物が使用されている｡ 本研究では, 実用化されている笛薬として安息香酸カリウムと過塩素酸カリウムとの混合物について熱分析し, 笛薬の反応を検討した｡ また, 笛音は波形, 周波数, 音圧を測定し, 笛薬混合比と筒長, 筒材を変化させた場合の笛音を比較検討し, 以下の結果を得た｡
(1)笛薬が笛音を出す混合比は安息香酸カリウム : 過塩素酸カリウム = 2 : 8, 3 : 7, 4 : 6の場合であった。また, 笛音を出す笛薬は線燃焼速度が0.4 cm / secかつガス発生速度が1500 cm / sec以上であった｡
(2)笛昔の基本周波数は2 kHz付近であり, 基本音に対し, 倍音が発生していた｡ また, 笛音の周波数と筒の長さは反比例した｡ したがって, 笛音は筒の共鳴により発生するものと考えられる｡
(3)筒材を変化させても笛音の周波数と線燃焼速度はほとんど変化しなかった｡ しかし, 音圧は筒材によって異なり紙筒で100 dB未満のものが, アルミニウム, ガラス, 塩化ビニルでは110 dB前後に大きくなった。