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1 Markets I: The Ecosystem and Exchange-Traded Markets市场在线 2 Markets II: Rates, FX and Credit市场在线 3 Markets III: Commodities, Energy and Crypto市场在线 4 Quantitative Methods方法在线 5 Derivatives and Volatility衍生品在线 6 Rates, Credit, XVA and Risk利率、信用与风险在线 7 Research Craft: Predictors, Backtests, Measurement, Portfolios研究在线 8 Strategies I: Equities and Futures策略在线 9 Strategies II: Volatility, Relative Value, Macro and the Bank Desks策略在线 10 Microstructure and Execution交易执行在线 11 Market Making and High-Frequency Trading做市在线 12 Machine Learning for Markets机器学习在线 13 Low-Latency Software技术在线 14 Networks, Hardware and Trading Infrastructure技术在线 15 Research, Data and Risk Platforms技术在线 16 The Desk and the Firm公司运营在线 17 The Industry: Firms, Roles and Careers职业发展在线 18 Interviews I: Maths, Probability and Speed职业发展在线 19 Interviews II: Markets, Trading Games and the Final Round职业发展在线 20 Interviews III: Code职业发展在线

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Physics · 术语表

什么是 Ultrasound and infrasound？

又称： ultrasound · infrasound

Definition 8.11 High School Physics · 第 8 章 — Signals and Waves

The human ear hears sound between about $20\,\mathrm{Hz}$ and $20\,\mathrm{kHz}$ (the ceiling drops with age). Sound above $20\,\mathrm{kHz}$ is ultrasound — bats hunt at $50\,\mathrm{kHz}$ , medical scanners image the body at a few megahertz. Sound below $20\,\mathrm{Hz}$ is infrasound, felt by elephants and seismometers.

Sound frequencies on a logarithmic scale (each step × 10). The ear hears from 20\, Hz to 20\, kHz; below is infrasound, above is ultrasound. — Sound frequencies on a logarithmic scale (each step $\times 10$ ). The ear hears from $20\,\mathrm{Hz}$ to $20\,\mathrm{kHz}$ ; below is infrasound, above is ultrasound.

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