Speak loudly to close more sales

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📝 Context

Topic: Customer Experience
For: B2C. Can be tested for B2B 
Research date: March 2025
Universities: Shanghai Jiao Tong University, University of Warwick, Stanford University, Southwest Jiaotong University, Fudan University

You’ve probably spent hours fine-tuning your sales pitch and what to say to customers.

But you should also pay attention to how you say it.

Science says that your tone and energy can shape whether, and how fast, customers buy.

P.S.: When selling, use concrete, specific language. It increases customer satisfaction and spending.

📈 Recommendation

Use a loud tone of voice when speaking to customers. For new customers, couple it with a bright and energetic tone. For customers who already know you, use a calm and stable voice.

People will be more likely to buy from you and will make the decision to buy more quickly.

🎓 Findings

• Salespeople using loud tones (e.g. a more intense and powerful voice) increase their likelihood of customers buying, and the speed of their decision. For new customers, a bright, energetic tone works best, while a calm tone is best for returning customers.

• As part of an online experiment and analysis of 8,920 sales calls for a high-end Chinese facial beauty treatment company (average spend usually $400+), researchers found that:

  • New customers:

    • Were 7.7% more likely to buy when a salesperson used a bright, energetic tone

    • Were 8.4% more likely to buy when the salesperson spoke in a loud tone

    • Thought a louder, more energetic voice made the salesperson seem 26.7% more excited about a deal

    • Planned on buying sooner after a sales call when spoken to in an energetic, loud voice

  • Existing customers:

    • Were 5.4% more likely to buy when the salesperson spoke loudly

    • 3% less likely to buy when a salesperson used a bright, energetic tone

    • Thought a loud voice made a salesperson seem 4.8% more competent

    • Thought an energetic voice made them seem 7.3% less competent

    • Planned on buying sooner after a sales call when spoken to in a loud, but not energetic voice

🧠 Why it works

• We use someone’s tone and volume as one of the factors to judge their emotions and abilities.

• When someone’s speaking to us in an energetic voice, we think they’re excited and passionate. This captures our attention when we’re looking at a brand or product for the first time.

• When someone speaks with a calm, measured tone, we assume they’re more competent and confident about what they’re saying. For a product we’re familiar with, this tone makes us more likely to trust someone when they’re selling.

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✋ Limitations

• While the effect does impact people’s decisions to buy (or not) a product, it doesn’t impact the quantity people buy (i.e. get people to buy more).

• The study was conducted in Mandarin with Chinese salespeople and customers. Different cultures might have different reactions to various tones and volumes. For example, American customers might be more accustomed to brighter and more energetic tones, while Japanese customers might find a loud tone too aggressive.

• The research looked at salespeople’s tone in isolation. It did not factor in how the speed or volume of delivery, or the content of the call, might impact how it’s received.

• The analysis focused on telephone sales. It hasn’t been tested, but it likely works the same way in person (e.g. retail stores).

👀 Real-life example

Online sales enablement platform Yesware highlights key tonal aspects for salespeople to focus on when selling.

❌ Issue: Their guidelines don’t talk about the importance of a powerful, intense tone or how different tones work best for new and returning customers.

✅ Solution: Yesware can optimize its sales training by:

• Highlighting the importance of a powerful, intense tone of voice when speaking to customers.

• Providing details on the types of pitch to use, with bright, energetic tones working best for new customers while a calm, measured voice works best for returning customers.

• Reinforcing the importance of building a human connection with potential customers to make the experience more personal, such as by asking them their name.

• Instructing people to use “I” instead of “We” when talking to customers to build empathy and a personal bond. 

🔍 Study type

Online experiment and market observation (analysis of 8,920 sales calls for a major B2C Chinese facial beauty treatment company between May and December 2019)

📖 Research

Whispers in Your Mind: The Role of Voice Features in Customer Acquisition and Retention. Journal of Marketing (March 2025)

🏫 Researchers

• Haifeng Xu, Shanghai Jiao Tong University

• Yi Ding, University of Warwick

• Yu Ding, Stanford University

• Qi Zhang, Southwest Jiaotong University

• Cheng Zhang, Fudan University

Remember: This is a new scientific discovery. In the future it will probably be better understood and could even be proven wrong (that’s how science works). It may also not be generalizable to your situation. If it’s a risky change, always test it on a small scale before rolling it out widely.

🎁 Bonus mini-insight

Check your knowledge from previous insights and case studies (for paid Platform members only). Read the full case study here if you are already a member.

🎓 Insight: Automating call centers

📈 Recommendation: People are okay talking to automated AI agents at call centers if you make the benefit of using the AI clear to them (e.g. faster response time or 24-hour support). Use AI agents for simpler, repetitive requests while saving human agents for more complicated tasks.

✋ Careful: Make sure you minimize how much (or often) a customer has to provide their information. Add their details to their “ticket” as they move through your phone tree between AI and human agents to prevent them from having to repeat the information multiple times.

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