A research group led by Hideaki Kato, a lecturer at Yokohama City University, observed the droplet distance and the amount of aerosol generated by singing and speaking in Japanese.In Japanese singing, the droplets spread about 60 to 70 cm in front and to the left and right, and it was found that fine aerosols were often generated in u vowels, ``ka'', ``ta'', ``ha'' and ``pa''.

 The new coronavirus infection (COVID-19) spreads mainly through droplets and aerosols.There are many reports of mass infection cases due to choirs, and the risk of droplets and aerosols is said to be high.

 This time, jointly with the All Japan Chorus Federation and the Tokyo Convenient Chorus Federation, we are recruiting 10 men and women from amateur choirs, ranging from boys and girls to seniors.A droplet observation study in Japanese singing was conducted using a clean room of Shin Nippon Air Conditioning Co., Ltd. and a droplet visualization device using laser light.

 In the Japanese song ("Praise of the Earth"), a maximum of 61 cm in front of the singer (111 cm in the German "Ninth") and a maximum of 70 cm in the lateral direction were confirmed.There was no gender difference in droplet distance, but the number of fine aerosols generated at the mouth by particle counter measurements was significantly higher for female voices than for male voices.

 Also, aerosol generation during Japanese reading aloud was low for a and e vowels, but significantly high for u vowels.For consonants, there were many aerosols in the "ka", "ta", "ha", and "pa" lines.No aerosols were observed when singers wore non-woven masks.

 In order to avoid inhaling droplets, it is important to secure a distance of 1 to 2 m or more to the left and right in front.Sufficient ventilation is necessary to prevent aerosols, but in places where the ventilation conditions are unknown, safe choir practice is possible by singing with the a vowel and wearing a mask.Based on this research, the "Guidelines for Preventing the Spread of Novel Coronavirus Infections in Choral Activities (All Japan Choral Federation)" were issued.

Paper information:[PLOS ONE] Expansion of droplets during speaking and singing in Japanese

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