350-401 Question #800: Real Exam Question with Answer & Explanation

Question

Which signal strength and noise values meet the minimum SNR for voice networks?

Options

• Asignal strength -67 dBm, noise 91 dBm
• Bsignal strength -69 dBm, noise 94 dBm
• Csignal strength -68 dBm, noise 89 dBm
• Dsignal strength -66 dBm, noise 90 dBm

Explanation

SNR for Voice Networks Explained

Option B is correct because it produces an SNR of 25 dBm (-69 dBm signal subtracted from -94 dBm noise floor = 25 dB), which meets the minimum SNR threshold of 25 dB required for voice networks. SNR is calculated by subtracting the noise value from the signal strength (ignoring the negative signs: 94 - 69 = 25).

• Option A yields an SNR of only 24 dB (91 - 67 = 24), falling 1 dB short of the minimum requirement.
• Option C yields an SNR of only 21 dB (89 - 68 = 21), falling significantly below the threshold.
• Option D yields an SNR of only 24 dB (90 - 66 = 24), also 1 dB short of the requirement.

💡 Memory Tip: Think "Voice needs 25" - for voice networks, SNR must be at least 25 dB. When calculating SNR from dBm values, simply subtract the smaller number (signal) from the larger number (noise floor), ignoring the negative signs. Any option giving you exactly 25 or higher passes the test!

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