“Opportunities for voice communication are decreasing every year, yet the number of contestants keeps increasing. That shows Japan’s commitment to phone manners will never fade,” Masayuki Yamamura, president of NTT East, one of the event’s corporate sponsors, said at the opening ceremony.

Formal phone answering is serious business in Japan, with many rules intended to head off offensive or awkward moments. A search on Amazon’s Japanese website found more than 60 books specifically on phone manners, and dozens more on business etiquette in general. Most appeared to be aimed at women, like “How to Talk Like a Workplace Beauty.”

A polite office worker picks up calls during the first or second rings; if, for unavoidable reasons, the caller is left waiting for three rings or more, an apology is in order. The conversation itself is carried out in a formal, honorific spoken form of language — peppered with exclamations like “I’m horrified to ask this request, but ...” At the end of the call, the receptionist must listen for the caller to hang up before putting down the receiver. Hanging up first is a serious faux pas.

Some experts explicitly tell women to speak in a higher voice than usual to sound feminine and energetic. “Think of the musical scale — do, re, mi, fa — and imagine speaking in fa,” says Akiko Mizuki, a business manner expert on AllAbout.com.

“It’s very difficult to be polite but effortlessly so. If you sound like a robot, you can’t put the caller at ease,” said Keiko Nagashima, manager at a call center for SBI Securities in Tokyo, which has been sending workers to compete in the competition for the last five years.

Ms. Nagashima’s protégé, Mika Otani, trained six months for the competition by writing out sample answers and practicing in front of a mirror to make sure she was properly opening up her larynx and articulating. But Ms. Otani, 26, does not plan to simply follow tradition. She considers herself a modern woman and shuns the high-pitched voice. As more women have taken on professional positions in recent years, she said, there has been a backlash against overly squeaky voices.

“I work at a financial institution, so I don’t want to sound like a cartoon character,” Ms. Otani said before the competition.