Audio Sample Kit

TDK's audio solution sample kit provides noise suppression and ESD countermeasures for microphone lines without degrading sound signals.

As society trends towards the Internet of Things and connected devices, smart appliances and consumer electronics are on the rise, including smart (or AI) speakers. The difference between smart speakers and conventional ICT devices is that with smart speakers, a person's voice becomes an interface to connect them with the device and the speaker's key components are microphones, which also act as sound sensors. TDK provides various types of MEMS microphones for these applications, which have been developed by applying TDK semiconductor micro-fabrication technology.

Important points to consider when using MEMS microphones include circuit technology and noise countermeasures so signal waveforms are transmitted with no distortion. If high-frequency signals from communication waves intrude into microphone lines, undesired sound known as buzz or buzz noise may be heard from speakers. Since this had in the past become a serious problem in telephones that used the TDMA (time division multiple access) system, it is generally referred to as TDMA noise. TDK has developed the MAF series of noise suppression filters for audio lines as components for use in countermeasures against such problems. Using the MAF series in microphone lines makes it possible to prevent TDMA noise without degrading sound quality. ESD (electrostatic discharge) countermeasures are also important to prevent the intrusion of ESD from human bodies into circuits through holes in the microphones. TDK's AVRF series ESD notch filters exhibit high-level noise suppression effects and can protect circuits from electrostatic discharges. Figure 1 shows an example of noise countermeasures in microphone lines using MAF series noise suppression filters and AVRF series ESD Notch Filters and their effectiveness. It can be clearly seen that in filter circuits that use both MAF and AVRF series products together, the insertion loss in cellular bands is even larger than in circuits that use only MAF products.

AUDIO-1-KIT combines TDK InvenSense MEMS microphones with TDK brand's noise suppression filters (MAF series) and ESD notch filters (AVRF series) specifically designed to combat typical issues in audio lines including suppression of TDMA noise while offering additional benefits such as improving reception sensitivity in cellular or Wi-Fi® communication.

Figure 1: Noise countermeasures in microphone lines using the MAF series noise suppression filters and AVRF series ESD Notch Filters

Figure 2: Example combinations of MAF noise suppression filters and AVRF ESD notch filters in microphone lines

Applications

• Noise suppression and ESD countermeasures for speaker and microphone lines

Additional Content Links

• TDMA Noise Countermeasures, Reception Sensitivity Improvement and ESD (Electrostatic Discharge) Countermeasures in Microphone Lines, Using Noise Suppression Filters and ESD Notch Filters
• TDK Sound Solution Product Portal