sound of footsteps in a deserted valley; rare,unusual guest; unexpected good news
? 這一消息真如～，使人歡欣鼓舞。This news was as rare as the sound of footsteps in a deserted valley and it filled the people there with joy.
空谷足音kong gu zu yin
footsteps one hears in a deserted mountain valley—valuable information or opinion that is dificult to come by
空谷足音kōnɡ ɡǔ zú yīn
在空山谷里聽到人的腳步聲。比喻非常難得的音信或事物。difficult to meet with, unexpected good news; rare, welcome appearance