Engineer's Selection Guide: How to Choose the Right Buzzer with Precision

1.Introduction
2.Acoustic Drive Method: Passive or Active?
3.How Buzzers Work: Electromagnetic vs. Piezoelectric
4.Core Parameter Checklist
5.Application-Specific Matching
6.Bestar's Technical Support and Competitive Advantages
7.Conclusion

Introduction
Sound feedback is essential in today's electronic devices. It's fundamental to the design. Buzzers are the fundamental part for visual status, error (user attention) and interaction feedback. Appearance of the indicator element does not depend on the user's perspective, or the lighting conditions in the environment. This ensures they are invaluable for safety and "hands-free" applications.
Buzzers market have a change. Design engineers are looking for particular attributes. Surface mount technology (SMT) is now expected, thanks to the advent of pick-and-place machinery for building printed circuit boards (PCBs). And extremely low power requirements are now essential, as battery-powered IoT devices require components in the microamp to solve their problems, not the millamp. An equally important aspect is a high sound pressure level (SPL) performance, which is essential in a wide range of industrial and outdoor applications where ambient noise levels are above 80dB.
As a component manufacturer, Bestar draws on its experience and expertise in acoustic design. Bestar has set industry standards for design, materials and testing in transducers, materials and reliability testing, which define best practice standards for a professional supplier of buzzers.

Acoustic Drive Method: Passive or Active?
The initial choice for a buzzer is the method of drive. It has implications for system design.
Active buzzers have an oscillator built-in. The role of the microcontroller is simply to provide a DC power supply. They don't need to generate an output signal from the host microcontroller. They're great alternatives to quickly build up working prototypes, embedded devices with limited resources and where you only need a single fixed-frequency beep. Alarm buttons, basic alarm systems and appliances are typical applications.
Passive buzzers need to be driven by an external square wave. It's supplied by the host system or a drive circuit. Flexibility is the pros. Engineers can vary the tone, musical scales or elaborate alert sequences by varying the drive frequency. Passive buzzers are a good choice for products with audio distinction. Passive buzzers enable a varied audio spectrum for smart homes, sophisticated alarm systems and process control HMI equipment. Passive buzzers can also draw less power when inactive, good for low-powered devices such as personal electronics.
The choice is a simple: an active buzzer for design simplicity, a passive buzzer for increased flexibility.

How Buzzers Work: Electromagnetic vs. Piezoelectric
The type of the transducer used defines the basics of its electrical and acoustic characteristics. The two most common types are:
Electromagnetic buzzers have a magnetic induction. A metal coil is energised in a magnetic field, displacing a metal diaphragm. This approach results in a warm rich tone with good bass response. Electromagnetic types are driven at lower voltages (typically less than 3V) and smaller sizes can be achieved due to their reduced size. Current draw is the main drawback. Instantaneous current is required to induce the voltage and current in the coil, which can cause high instantaneous demand from battery-powered devices during an alert.
Piezoelectric buzzers are based on different technology. Sound is produced by the expansion and contraction of a ceramic disc which is driven by an alternating voltage. The ceramic disc has very low current consumption. High impedance allows piezo buzzers to be easily driven by many different circuits. They have a wide voltage range (3V to 30V or more).
Bestar has been working to boost the performance of piezo technology. Their production process incorporates advanced ceramic materials, with controlled grain size. It results in better electromechanical coupling factors, resulting in higher levels of sound made by a smaller area. Bestar's ultra-thin piezo buzzers allows them to be incorporated in thin wearables and card-style products.

Core Parameter Checklist
The key parameters in choosing a buzzer interact. Failure to consider any can leave you with a component that far exceeds other criteria, but fails in application.
Sound Pressure Level (SPL): SPL is expressed in decibels at a specific distance (usually 10 cm). The desirable SPL is determined by the environment. About 65 dB in a small office. An industrial environment can require 85 dB or greater. (Be sure to check SPL at the listening position, not just from the data sheet.)
Resonant Frequency: All buzzers have a typical acoustic peak frequency. This needs to be tuned to the acoustic cavity of the enclosure. A buzzer that has excellent performance on the workbench can sound weak when it's placed into a closed cavity and cavity size does not match the resonant frequency peak. Bestar offers design engineers to help model the cavity.
Rated Operating Current: For battery-operated products like IoT sensors, asset trackers and wireless alarms, current draw when the buzzer is operating affects the battery performance. Determine the duty cycle of the buzzer alert cycle and total charge consumed. Choose the lowest current buzzers that achieve the desired SPL.
Package Size and Mounting Method: SMT buzzers can be pick, placed and reflowed. They requires maximum temperature tolerance of reflow, typically 500°F(260°C). Through-hole buzzers can be mechanically rugged, where strength against vibration is needed. Through-hole buzzers are common in industrial equipment, automotive retrofit modules, and power supply equipment.

Application-Specific Matching
There's no such thing as a best buzzer. Selection should be according to application needs.
Smart wearables and smart devices: Low stack height and size is the order of the day. IP ratings are important. For a fitness tracker or earable device, the buzzer should be rated to at least IPX4. 
Medical Devices: Compliance is top priority. Alarm tones need to comply with IEC 60601-1-8 alarms for medical devices. SPL drift between production lots is unacceptable as acoustic alarms are validated as part of device testing. A change in SPL can result in a re-test. 
Automotive Electronics: Wide temperature range and vibration resistance required. The audio range needed is from -40°F to +185°F(-40°C to +85°C) level or higher. Road vibration resistance in terms of solder joint reliability must be demonstrated. 
Smart Home and Security Systems: These are mainly in standby mode. Efficiency during its wait time is as critical as SPL during the alarm. The sound must overcome wall and background noises. 

Bestar's Technical Support and Competitive Advantages
Choosing a buzzer is rarely a datasheet-only exercise. The acoustic quality of the final product relies on details that need to be developed together.
Bestar can simulate acoustic wave progression inside by a given housing, the cavity size, port placement and size can be varied for optimal performance. This service eliminates design errors where an application-specific buzzer is not efficient because the housing does not match.
Materials and Process Reliability: Bestar's ceramic powder is processed to maintain precise impurity content and sintering characteristics. This results in stable piezoelectric coefficients batch to batch. 
Customisation: Customised designs are usually off-the-shelf. For unique applications, Bestar will offer custom frequency targets, nonstandard voltage ratings and lead changes. 

Conclusion
Buzzer selection can be easily mastered. The table below outlines the key considerations.

When choosing a buzzer, it's crucial to have a clear grasp of the drive method, transducer type, important acoustic parameters and requirements of the intended application. Active or passive, electromagnetic or piezoelectric, SMT or through-hole, these are only terms with meaning in relation to a product. By following the selection criteria described here, engineers can rapidly zero in on the right match and ensure that product requirements are met without mis-matching part to system needs. In applications where every dB of performance matters, or certification processes are highly sensitive, working with experts makes a difference. Bestar's Acoustic Design Team can be consulted at any time, including component selection and sound enclosure design. The best way to de-risk the design process and accelerate time to market is to consult early in the design process.